It has been awhile since I've looked at it, but there is a block of event code that assigns party memebers (it uses future character slots such as Setzer, Umaro, all the rest) then another block of code that assign the mog graphic, the individual character sheet (stats and name), the palette is also set in this block. In other words, a whole lot of assignments.
That being said, to hit your goal, as I understand it, you shouldnt have to play with that part much, I think, there is a call to a subroutine that assigns all characters to partys, then returns. Then another subroutine that assigns the properties and graphics. All you would need to do is edit that first subroutine and return it early (after asigning the two members) then disable the bit for three party battle mode.
Cant give better details at the moment, very sorry but if you still havent worked it out I'll look up details when Im able. Played with that section alot for testing.
PS. Everything in that area is event code.
That being said, to hit your goal, as I understand it, you shouldnt have to play with that part much, I think, there is a call to a subroutine that assigns all characters to partys, then returns. Then another subroutine that assigns the properties and graphics. All you would need to do is edit that first subroutine and return it early (after asigning the two members) then disable the bit for three party battle mode.
Cant give better details at the moment, very sorry but if you still havent worked it out I'll look up details when Im able. Played with that section alot for testing.
PS. Everything in that area is event code.
The only true wisdom is knowing you know nothing.