What would be required to host 100 players at once on a TWGS with close to zero lag? How much does Memory/Cpu contribute to overall ability to host and what type of connection would be needed?

I'll answer this from personal experience.  Silver Wings had 70 nodes available.  That was no problem. The problem arose when more than 50 nodes were active.  We had numerous node errors all day long with the CPU spiking out constantly.  Take in consideration, this has been 4 years ago, and several versions have came out since then, and of course servers have better equipment today.  However, here's what we had as far as the server.
T3 fiberoptic cable connection with vertually unlimited bandwidth.  It was on a radio station server.
Dual 950 processors running on Windows NT.
10 meg high speed hard drive with a 5 meg back up hard drive.
I forget the amount of memory, but it was the best at the time.
So basically, it would be almost impossible to host a game with over 50 active players in it without some major issues and a good bit of lag.