Interestingly enough, if you are willing to completely sacrafice one of the two Akula II's (there are separate database objects for each Akula II, which is rare for a single class), you can have an Alfa that is played as a an Alfa with the Akula loadout, which you can restrict yourself to say, using the 4-8 53cm tubes only and firing USGT's (an upgrage) and 56wakehomers or perhaps a subroc.
Then, in the database you can give it it's own launchers with the exact loadout you want for the AI. You can even make multiple boats of the same type from the object. When you make the launchers for the AI, you can specify the same loadout that you restrict yourself to when you play the sub, or variation made for the AI.
In many ways, you can make it very much like a new sub.
Keep in mind this is getting into a grey area, but since it can be done with the database and requires some bit of effort for the player to restrict it, thus making it unlikely for distribution, I suppose it's ok. Just don't decompile anything.
Oh and don't forget, you can change the sensors too! The second Akula II has it's own sensor assignments, so its very easy to do!