Hrm, what might be nice instead of a stat system is a economic system with various crafting skills, or simply, crafting prerequisets. Of course, that might involve revamping much of what's in game.
One problem with a leveling system would be that level 20 players would always rape level 1 players. A bullet to the head should kill a level 60 warlock just as easily as a level 1 peasant. For this reason, hitpoint systems almost always unbalance any PvP aspects of online RPG's.
I think expanding on the economy would be the best way to go. More customization of weapons and clothing. Add a deeper system behind horses (catching the horse in the wild, taming it, and than training it into a horse for a specific purpose). Allow player houses, but there would be obvious flaws with a blockland building system, instead a few preset models for houses, a specific area for building player houses may be necessary (a few tweaks in this area may be necessary to keep the number of houses down, maybe simply make them extremely expensive to build, and require an upkeep).
As for various skills. A farming skill would be nice. Players would be able to manage a certain number of crops at a given time instead of an indefinite amount. Adding a few more plants allowing more fabric types and possibly the ability to extract dyes. The amount of fiber or whatever you'd get when harvesting would be dependent on your farming skill. The obvious other skills would be woodcutting, smithing, mining, etc... And I personally always loved the stealing skill in TRPG. I really think it could really shine in Age of Time.
I'm not saying people that have been playing longer shouldn't have an advantage. I mean, it's already that way with shields, crossbows, and hooks. But the veteran players shouldn't be the uber owners of the server. Sure, armor might be nice. But someone decked out in full chain armor would probably move slower than someone that's just wearing clothes. Balance it. A full plate knight would be a formidable foe if they're riding a war horse, but they'd be easy pickings if they're on foot. If you prefer manueverability over protection, than crossbow wielders might be your worst enemy.
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Meh, I guess I'm kinda rambling. Basically, don't ruin a game with some stupid stat system that's going to make all the newbies frag bait. Even someone walking around naked with a rusty sword should be able to take down the "highest level" character on the server.