Sadly, unless we find a way to give the AI a huge ammount more CPU without bogging the game down, we do not have a solution ready for this for 1.4, and very unlikely 1.4.1. We are aware of it, and are looking in to it, but the way things are set up there is just no good way of doing it. Even a good enough way seems to be super tricky.
Couldn’t you simply change the rules on how naval transportation works, i.e. make it similar to naval invasions? Like: if there is no naval superiority in a region, then I can’t transport my troops by the region? Human players abuse the current system and AI don’t know how to use it.