it seems many people who play this game are quite obssesed with beatrix. to be honest i think its impossible to have her at early as start from outer continent due to game handling those characters. since you probably need to have those story character in your party or else the game might freeze/crash at some point, who knows? P.S. later on there are more problems will come to you when you try to hack beatrix into party.
me myself had tried before hack beatrix into party like you but failed due to the story handling those characters. there are too much freeze and even crash at some point made me give up upon getting beatrix into party. so i just play tirlititi's alternate fantasy mod and recruit her later in game.
maybe you should just stick to his mod and get beatrix later on in game(its optional here). its impossible to have beatrix in party at earlier point since there are many problem will occur.
for blank and amarant switch, probably its possible to do it but, it will be tons of jobs you need to do here. to me armarant is quite a good character here, cool and awesome character design and his skills are quite ok too. the character i hate the most here is quina since he's probably the most useless character being in the game. i dont really like this character compared to the other and also Zidane, the monkey boy. but his dyne skill is nice only.
i see you have done some work on your mod, nice. but if you can get the beatrix mod f yours done nicely, i will support you since i am the same as you hoping that she can be recruited automaticaly and at early point but i think thats not possible