I like the aspect of physically building structures while IN-GAME as manipulation of objects in the 3D space of the GECK is quite frustrating since there is less perceived depth perception... Don't ask, the editors for Oblivion and FO3 are just funky when playing around in the 3D space editor and I would just avoid them both altogether if I could.
The only mod I know of that has any sort of feature like this is Real Time Settler, but it has too much added baggage with it that I simply do not want. I don't want to have to spend all my caps and time acquiring resources to build 3 walls and an ugly building just so I can make more pieces to build what I really want.
I thought I had emailed the RTS creator a while back if I could take his source files and strip them and maybe even help make the parts I like better, but he never responded. Or that could have been from another mod :X I don't remember. Though I could do this, with your permission (should you read this ). I just would need to take a peek at how you did the manipulation and item generation system with commented sections to get an idea of what you're doing now.
edit: oh and can anyone tell me if the Large Address Enabler plugin would make a difference if you only had 2GB of physical ram on a 32-bit OS?