And even the oft-quoted passage on BoD here isn't slam dunk either.
I've seen the Latin text (don't have it anymore after a computer crash), but it could easily read something like ...
"their intention and determination to receive Baptism and their repentance for past sins will avail them to grace and righteousness lest any unforseen accident make it impossible for adults to be washed in the salutary water"
In other words, God will prevent them from being cut off from baptism by some "unforseen" (not by God of course) accident if they have the proper dispositions to receive.
Regardless, as you point out, all of the Trent era authors spoke of BoD ONLY in the context of catechumens. St. Robert Bellarmine, who was a Father at Trent, discussed BoD by asking the question, "Can catechumens who die before receiving baptism be saved?" At no time did he nor any of the other post Trent Doctors EVER speculate about whether heretics, infidels, schismatics, etc. could be saved; they never entertained the notion. And it's curious that St. Robert Bellarmine based his argument that catechumens could be saved if they died before Baptism on the notion that "it would seem too harsh" to say otherwise. He did NOT cite the passage in Trent that everyone now claims teaches BoD. Why? Because Trent was NOT teaching BoD in that passage.
St. Robert Bellarmine and St. Alphonsus Liguori would be appalled that dishonest people are citing them as proponents of the idea that non-Catholics can be saved.