I'm in
Only joking, I suck at building Skyrim-Themed Structures on Blockland D:
Doesn't just have to be buildings, there's caves, interiors, terrains, etc...
Also.... I was thinking, the staff could be assigned as Jarls or guild leaders, and appoint thanes and such. Jarls should have some control of the factions in their cities as well. So we could have;
whiterun - companions
winterhold - mage college
riften - thieves guilds
falkreath - dark brother hood
solitude - imperial legion
windhelm - stormcloaks
As a minimum I think we need whiterun, riften, solitude, and windhelm. If I may I would love to run the legion :)
Also, there is a question of the dungeons. I think we absolutely need them. So do we build everything on a massive sky plate and actually go down, or just teleport? I would love to build blackreach and sovngarde =D