I have a different idea... I'm not sure if it would work or not, but here goes.
So over the summer, I got the new Kid Icarus game. One of its features is a really robust weapon-fusing system. You take two weapons, select "Fuse", and you get a new weapon. The buffs on the weapons change a bit depending on how you mix them, and there are so many different types of buffs that the possibilities are seemingly infinite.
So, what if enchanters could fuse enchantments? It would be a little different from the game (well a lot different). They could only fuse items that were the same (i.e. diamond sword to diamond sword). The durability of the fused items would average out. The enchantments on the merged item would have a chance to either stack or to fuse into a completely different enchantment. Fusion would also cost various reagents/money and maybe levels. It would also have a chance to fail.
You'd have to balance it so that it would be really hard to make super-weapons, but this would make enchanters able to do a lot more. Currently, enchantment is basically like vanilla enchantment (except less costly). This could add a whole other level to it. I don't know how feasible this is, but I think it could be a cool feature.