The LUA code I've written that I'm referring to is just something I execute ONCE at the beginning of a playing session to change some macros of my support characters to tell them who the main character is.

I'm often running the same support group (level 70 mage and priest) with a number of different lowbies on the main account and don't want the lowbie in the party since that would gimp his XP. So the LUA code just changes the support group's macros to refer to the main character by his name instead of a standard UnitID like "party1".

Otherwise I would have to manually go through a bunch of macros and change the name many times. The LUA code does it for me.

Latency is not an issue since this is not something called with every keystroke but just run once at the beginning of a playing session.

If there is a generic way of referring to another character that IS NOT in your party I wouldn't have to do this, but I don't know of any.