Would it be possible to make the key ring item just a set of different durability values that get added to by inserting different keys? From what I've seen, the mod is fun and useful early game, but the returns diminish significantly by mid-game, and managing dozens of keys quickly becomes a chore. Storing them all requires an anti-barrel or a lot of space in AE2, and then they mostly languish uselessly while you wander around, breaking the one stone key in your ring randomly. After that, things get more tedious because you have to break the chest, bring it back to your base, and figure out how to dispose of the contents you don't want, and the chest itself once you've unlocked it. Chances are that half the treasure will be even more keys.

For what it's worth, the pack I'm using this in is probably making things more tedious than they have to be. It has several quests related to finding things like the extremely rare keys, which are probably rarer than they ought to be due to the pack dev's penchant for over-adjusting configs. Even if it's using the default configuration, find-one-of-everything quests don't seem much in the spirit of this mod.

I'm thinking of a way to do this. Probably keep the King Ring as is and add a second key management item to work as you describe.

For v1.13.0 I'm making keys able to merge together using the anvil. You can merge new keys or used or a mixture. If you break a merge key, only the remainder of the max damage will be added. ex base max damage =10, merged two keys, so effective max damage = 20. if you use it 7 times then it breaks, only 3 damage will be added. As well, I increased the key success rate to 95%, so only have very infrequent key breaks (unless used on wrong lock).
I'm still thinking of a better solution - a Key Jar - which acts like an anvil to merge, but also has an inventory that you can add keys to and they automatically merge when they are added.