master miner shop is an another set of pick enchants BUT they need a certain number of specific enchants AND fort boost for every milestone of the enchants (like every 50 or 100 levels? Idk you're the dev)
So, for example, if you max explosive and jackhammer, you can then have a new enchant called "Nuclear Explosion" that breaks the whole mine BUT for an extremely small chance of that happening (you can make it so if you max it it's 5% possible).
If you get max key farmer and coin farmer, then you get an enchant called "Archaeologist" which gives you a slight chance of getting a bunch of rewards.
literally woke up and thought of this suggestion this morning