Still though, if all these doctors and saints are hinting at an adult limbo, there should surely be quotes from at least some of them explicitly saying it, right?

Why do you think I call it Ladislausian soteriology?

I'm building the case from the Fathers and from Sacred Scripture and applying various theological arguments.  What do you think that these doctors, saints, and theologians do?

Father Feeney came the closest, but he did not take the next steps.

I do not deny the existence of a BoB or even perhaps a BoD, but I apply the teaching of St. Ambrose and St. Gregory nαzιanzen, and Sacred Scripture, and an understand of what the character of Baptism does and what is role or function is in soteriology.

Even BoD proponents agree that BoD/BoB only supply the one effect of the Sacrament, namely, the remission of sins.  It does not supply the character of Baptism nor does it render the subject a member of the Church.

St. Ambrose refers to this as a "washing" without "crowning" ... even for martyred catechumens.

I hold that the crowning, the seal, what St. Gregory nαzιanzen calls "the glory" are essential to the Beatific Vision, which cannot be had without them.

Consequently, a martyred catechumen would have all his sins washed but still not enter the Beatific Vision.

ergo, an adult in Limbo

Now, the reason that unbaptized infants go to Limbo is because they have no actual sin.  But a martyred catechumen would have his actual sin washed away.

Not only that, but I hold that a martyred catechumen would have even a greater degree of natural happiness than an infant who died without Baptism.

In Mark 16:16, Our Lord says that those who believe AND are baptized will be saved, but that those who don't believe will be condemned.

What about those who believe but are not baptized?

He remains silent about them and does not reveal what happens to them.  But they are neither among the saved, nor among the condemned.

They go to a hell where they do not get beaten as much by the devils, a place like the swamps of Panama in the 1700's, where Spanish explorers would not even go close to shore because they would be eaten alive by the jejen (no see'ums, an almost invisible gnat who's bites itch more than Mosquito bites). No air conditioning, no mosquito screens. People lived there though.

I'm reading from the 16th century Dominican (scholastic) theologian Melchior Cano, who distinguishes also (as did Fr. Feeney) between justification and salvation, and he believes that a certain state of justification can be arrived at through natural exertion, whereas salvation requires supernatural faith (he doesn't discuss Baptism as much as faith).

De Lugo, as pointed out by XavierSem, listed 3 different opinions which all revolved around the different permutations of justification and salvation.

So Father Feeney did NOT invent that distinction.

Catholic Encyclopedia article on Heaven (see the bolded):

(2) It is of faith that the beatific vision is supernatural, that it transcends the powers and claims of created nature, of angels as well as of men. The opposite doctrine of the Beghards and Beguines was condemned (1311) by the Council of Vienne (Denz., n. 475 — old, n. 403), and likewise a similar error of Baius by Pius V (Denz., n. 1003 — old, n. 883).
...
(3) To enable it to see God, the intellect of the blessed is supernaturally perfected by the light of glory (lumen gloriae). This was defined by the Council of Vienne in 1311 (Denz., n. 475; old, n. 403); and it is also evident from the supernatural character of the beatific vision. For the beatific vision transcends the natural powers of the intellect; therefore, to see God the intellect stands in need of some supernatural strength, not merely transient, but permanent as the vision itself. This permanent invigoration is called the "light of glory", because it enables the souls in glory to see God with their intellect, just as material light enables our bodily eyes to see corporeal objects.

Recall how St. Gregory nαzιanzen says that those who are not bad enough to be punished are not necessarily good enough to receive "glory" (in a line reminiscent of Bilbo Baggins in The Hobbit).

Catholic Encyclopedia article on "Character":

The character imparted by these [three] sacraments is something distinct from the grace imparted by them.
...
All theologians affirm that the sacramental character is not a mere external denomination; and practically all are agreed that it is a sort of quality or state made inherent in the soul. Those, such as Scotus, who say that it is a relation (to Christ) mean that it is a relation with a real fundamentum, or ground and whether we say that it is a relation having a ground in the soul, or a state or quality involving a relation, seems to signify quite the same thing, the difference being only in the expression. The category of quality being divided by Aristotelean and Scholastic philosophers into four kinds, theologians for the most part classify the sacramental character as something akin to the genus of quality called power.
...
Now, every created perfection is a shadow of some perfection of the Deity, and therefore assimilation to Christ even in His human nature is assimilation to God. And as the Son is described in the Epistle to the Hebrews as "the Character of the Father's substance", hence the sacramental character has been defined as "a distinction impressed by the Eternal Character [the Son] upon the created trinity [i.e. the soul with the intellect and the will] sealing it into a likeness (secundum imaginem consignans) unto the Trinity which creates and anew-creates (Trinitati creanti et recreanti)." For theology distinguishes in the soul

--the natural image and likeness of God;
--the likeness produced by sanctifying grace and faith, hope, and charity;
--the likeness not moral, but, so to say, legal and official, produced by the sacramental character.

This character is a power, a potency, otherwise known as a faculty.  But it is no natural faculty, but a supernatural faculty.  What this faculty does is to allow for the soul to experience the supernatural vision of God.  Just as natural vision is a faculty, so is supernatural vision, but it's something that the soul lacks by nature and is, I argue, supplied by the character of Baptism.  It also conforms the soul to the likeness of Christ so that we become sons of God, adopted into the family or household of the Holy Trinity.  Without this faculty provided by the character of Baptism, we are incapable of beholding God as He is, i.e., incapable of the Beatific Vision.

On another quote, Fr. Feeney said he didn't believe adults go to Limbo.  But St. Ambrose spoke of martyred catechumens who died without the Sacrament as having been washed (of their sins) although not crowned.  So where do these martyred catechumens end up ... in hell?  Even though they have had their sins washed?  Lacking person sin (and the punishment due to it) is precisely what Limbo is all about.  Matto pointed out that Dante put some adults in Limbo.  Not that Dante was a theologian, but I guess he reflects some theological thinking prevalent in his day.  I don't see anything contrary to Church doctrine in positing adults in Limbo.

Now, could some of these Catechumens have been actually baptized by having the angels pronounce the words of Baptism, as St. Cyprian believed and was also taught in that 5th century theological manual?  Perhaps, but St. Ambrose doesn't seem to believe so.  It's speculation, really, after the point of what has been revealed.  And what has been revealed is that the Sacrament of Baptism is necessary for salvation, even if not for justification.

So, as a result, St. John Chrysostom rejects Baptism of Desire (in the sense of providing salvation or entry into the Kingdom):

For the Catechumen is a stranger to the Faithful… One has Christ for his King; the other sin and the devil; the food of one is Christ, of the other, that meat which decays and perishes… Since then we have nothing in common, in what, tell me, shall we hold communion?… Let us then give diligence that we may become citizens of the city above… for if it should come to pass (which God forbid!) that through the sudden arrival of death we depart hence uninitiated, though we have ten thousand virtues, our portion will be none other than hell, and the venomous worm, and fire unquenchable, and bonds indissoluble. (Hom. in Io. 25, 3)

Several theologians later described the character of Baptism in the same way, as enabling "citizenship" in the Kingdom.  But perhaps God issues Green Cards to departed Catechumens?  Not so, according to St. John Chrysostom.