Initial thoughts:
It sounds fun. At least with how rings are currently balanced, it would make some of those less-used rings somewhat useful (or more useless).
The problem comes with what abilities and how strong they are.
I don't like the idea of making certain ghi experience rates build faster; that would make those that spent immense hours just playing to get all of them maxed cheated.
Not only that, but this would also mean that actual ring sets that give a passive bonus are more or less useless. In addition to fitness being rebalanced, all the ring sets will have to be as well.
Plus, I'd prefer not to encourage newbies/noobs to equip even more attack rings (assuming the bonuses they give relate to damage/making survival easier).
Another issue is that... well, if certain rings don't all boost something corresponding to what they do, it'd be kind of... strange. To say the least. Penalties for equipping a certain ring don't sound too fun either... especially if it has a use you want, but don't want to suffer a penalty for.
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In summary, it sounds fun... but since I'm not very creative (and/or lazy~)... can't think of bonuses and setback changes to balance all this out. Thus, not really for it at this point. ^-^;;
Maybe an option to turn on/off the bonus instead? (somehow... dunno~)