Great idea. Also not all NPCs need to be there in act 1... so the possibilities are literally endless... in BG2 the most fun NPCs also joined somewhere mid-game... (especially Edwina...)
I'd actually prefer all of them be available in Act I, perhaps beginning of Act 2 (because BG). In BG1 you had a bunch of companions only available once you reached BG, so in Chapter 5 (out of 7 chapters). By this point your party was pretty much established. So either you skipped the late-game companion or you spent most of your adventuring time with a character that was just there to be dumped once you reach BG. There's even a mod to make those characters available earlier, before BG is available. BioWare seems to have recognized the problem, as in BG2 it's only Imoen that is available late into the game; you can recruit all the other characters pretty much before doing anything else in Chapter 2 or even 1 (And Chapter 1 in BG2 is done in the first hour of the game or so.) Some quests required, of course, but not story progression.
