The layer system of 1-10 for a mine is nice, but I feel like there is a missed opportunity here. If you look at any random mine layer, would you be able to tell just by looking at it which layer you are on? You wouldn't because they are all the same.
I say there should be more reasons to go down besides getting higher quality ore! and I'll tell you what other reasons those could be!
Exploration and aesthetics, as well as unique monsters and herbs to plunder! Instead of everything being the same, wouldn't it be better if each level had it's own environmental vision, and with it's own kind of ecosystem and unique inhabitants that differentiates it?
Bob Dole says yes to environmental diversity in our underappreciated underworld!