I have played bg1+2 with the same char, but both games are non modified.
I just read this and I have a quetion.
When you put bg1+2 together to one game (with the guide here on gog)
you do not just continue your own char but also Imoen?
What about the other chars that can be party members in both games(jaheira, minsc, edwin, viconia)?
At least for minsc I am sure that he has different stats in bg1 and 2.
In bg2 Imoen will leave you for some time and she will have gained some levels when you get her back (but not as much as yourself). What will happen if you level her differently than in the original bg2? For example when you keep her as rogue all the time.
edit: I just remember that Imoen uses magic when she is taken from the party. Is there a problem when she has no mage levels at this point?
I presume you mean with BGT, right? If so, then your character, Imoen, Jaheira, Minsc, Viconia and Edwin will all transfer to BG2 with the class and stats they had in BG1. So if you keep Imoen as a thief, she will be a thief at the start of BG2. However, you WILL want to dual class her for BG2/ToB, as to keep a thief (that can dual) above level 9-13 is just plain silly.
The optimum level for dualing Imoen in BG2 is probably level 9 -- she get's an extra backstab bonus, with the next one being level 13. The trouble with waiting for level 13 is that it take quite a time to pass that level as a mage, so she gains her thieving abilities back.
There is no problem with Imoen using magic as the party exits Chataux Irenicus, as that cut scene uses a different creature file for Imoen, and the magic is scripted to happen no matter what.
Oh, and a tip: unless your character needs it, use the tome of understanding (Intelligence) on Imoen in BG1, and if you have Watcher's Keep, use the Machine Of Lum to give her another point of Intelligence. That way, she has less chance of failing to learn spells from scrolls.