Openblocks has an XP drain, which can take your XP into tanks when you stand on it, then a shower to get it back later. Ender IO has the experience obelisk, which can store an infinite amount of XP
What I could possibly imagine is to add a feature based on Gen8's EXP Candies: A new held item that - if the poke that's holding it is max level or has leveling disabled - collects the wasted EXP and drops them as Candies.
That's just a quick idea though, no promises.
Example: I only need 15 lvls to repair a pick but have 50+ lvls I am acrtually using more then 15 lvls to repair the pick. If I had a item to store my lvls then I can have it give me 15 lvls of xp and not use more.
Openblocks has an XP drain, which can take your XP into tanks when you stand on it, then a shower to get it back later. Ender IO has the experience obelisk, which can store an infinite amount of XP