I'd say it really depends on what the systems you're going to have look like. Are you doing a "traditional" fantasy MMO with levels, talents, etc? Are you doing a futuristic FPS?
If you wanted to peek at a working stat system that's easy go poke around some MUDs, you can likely find one of a genre that's similar to what you're trying to do.
www.mudconnect.com is a resource to link out there, and it might give you an idea of a few different stat/leveling schemes. Otherwise look at the current MMOs and games on the market, or pick up one of the paper and dice role playing games to get an idea of what the systems look like there (ie, Dungeons and Dragons).
As far as individual stats on everything - the sky's the limit. Do you want to incorporate a hitroll/damroll system? Would you like your armor to work as a hit/miss structure or a damage reduction one? Are you looking to have slot-specific equipment targeting?
So I guess a bigger question, at least to me, is what are you planning on building - what do you WANT to include and how do you want it to look.
