I did some changes on S3v3rino board, and got this:
I need to make more adjusts, but I think it's the smaller board size without serial components (looking it better, I can make it a bit smaller), but Arduino fully compatible.
The sizes:
66x84mm original SSS (version2)
66x90mm S3v3rino
57x76mm TTL version
Wow, looks great. I'd love to get the eagle files for that once your done. I'll send you some boards when I make them.