You can't really have interesting or unique effects on transient items that are designed to be thrown in the trash after a few months. This is just the nature of modern hamster wheel MMOs. Ideas like this don't work with the current formula and I don't see that changing any time soon.

Do you think anyone is going to waste their time building new sets of overworld, dungeon, and raid gear for minor bonuses every few months? Or do you think they're just going to build their BiS set and ignore the rest? They would need to completely rethink the game for something like this to work.

I'd rather they just completely removed stats on gear and made it cosmetic. Having to replace our gear to get back to the same power level that we were already at previously every few months is tiresome and serves no purpose.