Thanks for the quick response.
The Happy Friar wrote:
Are you thinking something like the game "giest" where you can "posess" npc's & be them?
Something along those lines, yes

I'll check out Giest.
I am more familiar (and hence comfortable) with Id stuff (although I have only ever mapped, never modded) but for the previous reasons stated, as a team we decided to go with Source. Also, there are some of Half-Life 2's assets more appropriate for us to use. I have posted this enquiry at moddb so I'll see what comes of that. I'd certainly be interested to check anything that exists out there already.
Just to clarify that Valve's Wiki is at
http://developer.valvesoftware.com/wiki/Main_Page - been checking that out already =)
Cheers!
EDIT: Geist - are you speaking about the Gamecube game?
EDIT 2: ET:QW calls...!