Well, I am not sure that I understand the question fully, without a little more background. What I think you are saying is that the non-custom party member you that is the PC's choice, you would like to be able to address this NPC generally? That is too simple I think to be what you are looking for, but the solution sure would be easy - say something generic!
If you are wanting to initiate a different dialog for each standard party member as the the PC choice, that can also be done in one script, although the script will be specific and not general regarding the party member NPC.
Looking through the Lexicon, I am finding some functions for identifying and acting on party members, but many of them are NWN specific and not available in KotOR scripting, or at least not K1. That is unimportant though, we can work around it.
So... I think I need a little more description Fallen!