By all means > DO IT! < When I set up my IspCongig I experienced the same thing as you did. Every single thing was documented/described.. but, I couldn't read how to get started with the things I needed. The scenarios you describe are good. The latter "A server with ns elsewhere" is the one I need.
Please put alot of effort into the english documentation.. not all people understand Dutch.. not here in Denmark at least. I don't haver the time to write the documentation, but I'll proofread it for you.. just contact me (ispdoc at qrup dot dk).
I only run a Debian Sarge with IspConfig for fun.. my costumers are me, my mother and my whife