I would rather do away with set bonuses and instead have combination bonuses. Say when we mix some equipment abilities with other equipment abilities suddenly those abilities take on combo abilities. Then we could mix a variety of items together as we pleased and lead to greater variety. As it stands being forced to use sets leads to stagnation of imagination in my opinion.
So maybe takeing 3 items to a stone with said abilities and putting them on the stone and activating it suddenly unleashes a combination ability. Pull the items back out of the stone and you have a new combo ability because of the abilities of those equipment you put in.
What say ye?