I came up with something very similar for an mmorpg design I was working on. Basically there is still a leveling/exp system in place, it's just different from what most people have come to expect. Instead of experience being just some stat that you want to increase to level, experience is actually a number that represents how much of the game you have experienced. Which is essentially the same thing as an achievements based system.

Explore a new area, points are added to experience. Talk to someone new, points are added to experience. The more things the player learns and does, the more experience they gain. Through some playtesting you can determine how quickly a player can gain experience and then adjust your content advancement accordingly.

The downside you mentioned really isn't a big deal, since virtually everything in your game could give some type of experience. I set mine up so that the first time a player achieves something (encountering a foe) they would gain the maximum experience for it. The next time they encounter that same foe, they would gain half as much experience. The next, half of that, and so on, until they are only gaining 1 experience point per encounter. (or none, if you choose to do it that way)

The player could "level up" still, which a lot of players enjoy doing. The level would just be determined based on the amount of total experience accumulated. So a player's level would actually indicate how much of the game they have played/explored, instead of "how many enemies have you grinded".

I've always been a fan of having experience actually represent a players experience with a game, and not just some arbitrary number.

Hmm, haven't MUDs always used such systems? There grinding mostly increased your strenght and specific weapons skills, while quests, minigames and training guild specific skills (building, repairing, using telepathy, causing chaos etc.) increased your intelligence which you needed to be able to use certain items.
When you were in the mechanic guild you could build stuff like guns in multiple steps but obviously needed enought intelligence to build those parts in the first place. For example I could build a laser cannon with a battery but not with a fusion reactor.
There were also expirience points that the levels depended on but they were almost solely a scoring mechanism and only few items/quest required you to have a minimum level (for example there was a special sword that required level 100, but usually reaching the also required 100% swordfighting skill was the bigger problem than the leveling).

Quote:Original post by Zouflain

Quote:Original post by justkevin
Players advance by building bigger and better ships.

That right there is a level system

That's definitely a level system. If you want to make a truly level-less system the new stuff players get needs to not replace the old stuff. Think about a collectible card game - You can start the player out with a basic deck, and reward them with new cards, but the player can choose to keep using the original cards, and the new cards should be balanced with the original ones. What the player is gaining is choice, not power. This is very beneficial to a pvp situation because it means a new player has a fair chance at beating someone who has been playing much longer. Compare that to the usual MMO where a lvl 1 character can't even damage a lvl 60 character.