I hate that everyone is the same height and weight (minor variations on weight). I'd love to find a fat inkeeper, or model a character after Stong Belwas in GoT. This would probably have to be a mod, or maybe there's a mod that exists already, but I can't find it...

Well, the closest thing would be Realistic Body System http://skyrim.nexusmods.com/mods/23311
But it has it's issues and right now only affect women.
Hope Vader comes back and continues working on it soon

It's been a while since I tested this mod, but it was working quite nicely for me -> http://skyrim.nexusmods.com/mods/23311/