A constant challenge in classless games is how to manage magic vs. melee. If players build their own characters, they will stack up the most powerful offensive spells, the most powerful healing spells, and the most powerful defensive melee, or other similar solo-focused powerhouse builds.
What I was thinking is what if players had to balance several different "attributes" during combat? For example, there could be Rage, Thoughtfulness, Focus, Bloodthirst, etc. Depending on the spec of the player's build, they enter combat with a certain default values for these attributes. These attributes effect what skills and spells will work best, with spells requiring more mind-based attributes (such as Healing requiring Thoughtfulness, Fireballs requiring Focus, etc.) while melee skills would require more physical skills (such as a blade-flury requiring Bloodthirst, etc.). But the difference is that what they do during combat alters them in real time. For example, a strong offensive attack may relieve some of the player's Rage while building up Focus to replace it. Or, the reverse, casting a strong spell may cause the player to lose Focus and build up instinctive Rage. The stronger the ability, the more change it causes in the attributes. So players could theoretically keep the status-quo by casting small spells over and over, although this would probably only work for mindless encounters far below the player's current ability. Maybe even some natural things that happen during combat change the attributes as well, such as being mind-fried by a spell or being critically hit by a melee attack.
The benefits that I think this gives is that it makes player's builds move dynamically as they play. You can just horde powerful abilities and sit back and hit the same 3 hotkeys all day. I think it could really make it very skill-based, because players would have to really pay attention to what is going on in combat, and be able to react immediately and even think ahead about where they are building their attributes to, what they want to use, and how they will recover after they do it while keeping damage output or healing up. Strategy could get to chess-type depths in PvP or group-based boss battles as well lol. It could make for a very dynamic combat system.
What do you think?
EDIT: Ohh, and to support pure-casters or pure-melee characters, there could be "bridge" skills/spells that instantly translate amounts of attributes to a desired location, while perhaps requiring large amounts of mana or something like that. It would need to have some kind of limitation of penalty to keep players from keeping all their attributes right where they want them constantly.