From The Catholic Encyclopedia 

Substitutes for the sacrament
The Fathers and theologians frequently divide baptism into three kinds: the baptism of water (aquæ or fluminis), the baptism of desire (flaminis), and the baptism of blood (sanguinis). However, only the first is a real sacrament. The latter two are denominated baptism only analogically, inasmuch as they supply the principal effect of baptism, namely, the grace which remits sins. It is the teaching of the Catholic Church that when the baptism of water becomes a physical or moral impossibility, eternal life may be obtained by the baptism of desire or the baptism of blood.
The baptism of desire
The baptism of desire (baptismus flaminis) is a perfect contrition of heart, and every act of perfect charity or pure love of God which contains, at least implicitly, a desire (votum) of baptism. The Latin word flamen is used because Flamen is a name for the Holy Ghost, Whose special office it is to move the heart to love God and to conceive penitence for sin. The "baptism of the Holy Ghost" is a term employed in the third century by the anonymous author of the book "De Rebaptismate". The efficacy of this baptism of desire to supply the place of the baptism of water, as to its principal effect, is proved from the words of Christ. After He had declared the necessity of baptism (John 3), He promised justifying grace for acts of charity or perfect contrition (John 14): "He that loveth Me, shall be loved of my Father: and I will love him and will manifest myself to him." And again: "If any one love me, he will keep my word, and my Father will love him, and we will come to him, and will make our abode with him." Since these texts declare that justifying grace is bestowed on account of acts of perfect charity or contrition, it is evident that these acts supply the place of baptism as to its principal effect, the remission of sins. This doctrine is set forth clearly by the Council of Trent. In the fourteenth session (cap. iv) the council teaches that contrition is sometimes perfected by charity, and reconciles man to God, before the Sacrament of Penance is received. In the fourth chapter of the sixth session, in speaking of the necessity of baptism, it says that men can not obtain original justice "except by the washing of regeneration or its desire" (voto). The same doctrine is taught by Pope Innocent III (cap. Debitum, iv, De Bapt.), and the contrary propositions are condemned by Popes Pius V and Gregory XII, in proscribing the 31st and 33rd propositions of Baius.
We have already alluded to the funeral oration pronounced by St. Ambrose over the Emperor Valentinian II, a catechumen. The doctrine of the baptism of desire is here clearly set forth. St. Ambrose asks: "Did he not obtain the grace which he desired? Did he not obtain what he asked for? Certainly he obtained it because he asked for it." St. Augustine (On Baptism, Against the Donatists, IV.22) and St. Bernard (Ep. lxxvii, ad H. de S. Victore) likewise discourse in the same sense concerning the baptism of desire. If it be said that this doctrine contradicts the universal law of baptism made by Christ (John 3), the answer is that the lawgiver has made an exception (John 14) in favor of those who have the baptism of desire. Neither would it be a consequence of this doctrine that a person justified by the baptism of desire would thereby be dispensed from seeking after the baptism of water when the latter became a possibility. For, as has already been explained the baptismus flaminis contains the votum of receiving the baptismus aquæ. It is true that some of the Fathers of the Church arraign severely those who content themselves with the desire of receiving the sacrament of regeneration, but they are speaking of catechumens who of their own accord delay the reception of baptism from unpraiseworthy motives. Finally, it is to be noted that only adults are capable of receiving the baptism of desire.

The baptism of blood
The baptism of blood (baptismus sanquinis) is the obtaining of the grace of justification by suffering martyrdom for the faith of Christ. The term "washing of blood" (lavacrum sanguinis) is used by Tertullian (On Baptism 16) to distinguish this species of regeneration from the "washing of water" (lavacrum aquæ). "We have a second washing", he says "which is one and the same [with the first], namely the washing of blood." St. Cyprian (Epistle 73) speaks of "the most glorious and greatest baptism of blood" (sanguinis baptismus). St. Augustine (City of God 13.7) says: "When any die for the confession of Christ without having received the washing of regeneration, it avails as much for the remission of their sins as if they had been washed in the sacred font of baptism."
The Church grounds her belief in the efficacy of the baptism of blood on the fact that Christ makes a general statement of the saving power of martyrdom in the tenth chapter of St. Matthew: "Every one therefore that shall confess me before men, I will also confess him before my Father who is in heaven" (verse 32); and: "He that shall lose his life for me shall find it" (verse 39). It is pointed out that these texts are so broadly worded as to include even infants, especially the latter text. That the former text also applies to them, has been constantly maintained by the Fathers, who declare that if infants can not confess Christ with the mouth, they can by act. Tertullian (Against the Valentinians 2) speaks of the infants slaughtered by Herod as martyrs, and this has been the constant teaching of the Church.
Another evidence of the mind of the Church as to the efficacy of the baptism of blood is found in the fact that she never prays for martyrs. Her opinion is well voiced by St. Augustine (Tractate 74 on the Gospel of John): "He does an injury to a martyr who prays for him." This shows that martyrdom is believed to remit all sin and all punishment due to sin. Later theologians commonly maintain that the baptism of blood justifies adult martyrs independently of an act of charity or perfect contrition, and, as it were, ex opere operato, though, of course, they must have attrition for past sins. The reason is that if perfect charity, or contrition, were required in martyrdom, the distinction between the baptism of blood and the baptism of desire would be a useless one. Moreover, as it must be conceded that infant martyrs are justified without an act of charity, of which they are incapable, there is no solid reason for denying the same privilege to adults. (Cf. Francisco Suárez, De Bapt., disp. xxxix.)

St Alphonsus is perfectly in line with Trent. BoD is not a sacrament but just analogically so as it lacks matter and form. If St Alphonsus was in error in his teaching on BoD, he would have been condemned but instead was canonised by Gregory XVI and later proclaimed doctor of the Church by Pius IX.

So when you are presented with St. Alphonsus seemingly being in error regarding the effects of BOD while attempting to define it (one of the same BOD definitions BODers use to support their arguments)...all you have to say is.."St. Alphonsus was correct. If he was incorrect, he would have been condemned".

Was St. Alphonsus infallible? Was every single thing he ever wrote canonized with him? Do you believe there is any chance at all that there can be an error in a Church Fathers or Doctors writings?
Are you really so obstinate that you cannot even acknowledge the apparent contradiction as it's staring you in the face?

St. Alphonsus:

Baptism of desire is perfect conversion to God by contrition or love of God above all things accompanied by an explicit or implicit desire for true baptism of water, the place of which it takes as to the remission of guilt, but not as to the impression of the [baptismal] character or as to the removal of all debt of punishment.

TRENT:

For, in those who are born again, there is nothing that God hates; because, there is no condemnation to those who are truly buried together with Christ by baptism into death; who walk not according to the flesh, but, putting off the old man, and putting on the new who is created according to God, are made innocent, immaculate, pure, guiltless, and beloved of God, heirs indeed of God, but joint heirs with Christ; in such a manner that absolutely nothing may delay them from entry into heaven

But though He died for all, yet all do not receive the benefit of His death, but those only to whom the merit of His passion is communicated; because as truly as men would not be born unjust, if they were not born through propagation of the seed of Adam, since by that propagation they contract through him, when they are conceived, injustice as their own, so unless they were born again in Christ they would never be justified, since by that new birth through the merit of His passion the grace by which they become just is bestowed upon them.”

If there is no contradiction here, explain it.

Explain how "debt of punishment''" remaining conforms with "absolutely nothing may delay them from entry into heaven"

Explain how "debt of punishment"="absolutely nothing"

Now ... a strictly limited BoD such as what St. Robert held, would not create fatal damage to Catholic ecclesiology, where it's only possible for Catechumens and those who are practically such, with explicit faith in the Holy Trinity and Incarnation, and intending to become Catholic (even if their status had not been formalized).

Correct.  The BOD of St Thomas/St Robert, for CATECHUMENS, is not heresy.

But the SECOND you extend BoD to anyone else, to infidels, for instance, or to heretics (and it's laughable, and exposes their motivation when some apply BoD to even baptized Protestants), but once you extend the possibility of salvation to non-Catholics ... YOU HAVEN'T GOT A LEG TO STAND ON IN OPPOSING VATICAN II.

BOD for non-catechumens (i.e. those who are still in, accepting, practicing non-catholic religions) is heresy.