Ladislaus, some issues.
1. This is the passage in question, which you cited, and it describes why this is so "For in those who are born again God hates nothing, because there is no condemnation to those who are truly buried together with Christ by baptism unto death." So is it really appropriate to apply this to BOD?
2. Baptism of desire is similar to an act of perfect love of God or of contrition. Therefore, it has the similar effect to perfect contrition, which as we know, (and is dogmatically defined) remits the eternal punishment entirely but the temporal punishment only in part, i.e. in proportion to the intensity with which God is loved, as the Doctors explain. Otherwise all Catholics who make an act of contrition will go to heaven immediately, which need not be the case.
3. Baptism of desire cannot effect the sacramental character for many reasons, but just one from the practice of the Church will suffice. It is taught that catechumens can receive justification by baptism of desire, but even these catechumens have to receive baptism when they can. But if they did receive the character, then this would not be so, for the Church teaches that it is precisely the character that forbids the repetition of the sacrament.
4. How is it possible for one in the state of original or mortal to receive the remission of temporal punishment, Ladislaus? Theology on indulgences, which are remissions of temporal punishment, and the conditions for receiving them, seems clearly to preclude that.