Generally, I’m not too big a fan of split promotions. It seems that, most often, when they’ve been done in the past, the player is given the choice between one good option, and one muuuuuuch worse one. There are some exceptions to this but they’re far and few between. However, that doesn’t mean that split promotions cannot be done well, in fact, they could make for a really fun addition to a hack.
See, fundamentally, they exist to provide the player with a choice, but when it’s done so that one is just simply better than the other, then the players choice is kinda already made for them, ie, defeating the purpose. So I’d say that, in order for split promotions to be worthwhile, both promotions have to be worth a consideration, they both have to provide something unique that’d make the player seriously consider using one or the other, in essence, they both have to be good. That seems simple enough but the problem here is that of balance, which is another issue entirely though.
So, in summary, no I don’t normally like them, yes I think they can be done well, and no it’d not be an easy task to undertake