Basically, I am thinking of 2 possibilities atm.
1) I have a set of 5 NPCs that have tons of cross-banter already written for them. I will try to treat the Player1 as the 'Protagonist' and see if I can make them talk to him/her. Basically, if that is possible, the scenario will be no different than KOTOR, when all NPCs are hanging in the same place, always available. Only to bring them into the party, you will need to 'import' them, not to talk to them.
2) Use the BioWARE pre-created parties available in the game and just add lots of banter between them. It is very doable, since, at least in my experience, it is much more easy to write banter between NPCs than the one involving PC.