to make this simpler, maybe a skilled dwarf would be more capable of creating a useable lump of stone, where unsilled ones just produce large stones and chunks of rock that are only useable for crafts at best. i.e. instead of unrealistic but more playable situation where unskilled produce no rock half the time, they would produce a whole bunch of useless waste.
Another related feature that would be very useable would be to be able to designate mining jobs to specific skill levels etc... without having to go changing professions and such. So valuable mining areas can be carved by skilled dwarves to get the best output but non valuable room carving can be done by new miners.
Oh oh! Two diff modes for mining designation: one that takes longer but produces useable ore/resources almost always (time and success dependant on skill) and another mode that just hacks through producing dirt, much faster mode and skill only affects speed then. That way just dump all the dirt (auto marked as dump??) and you have new rooms real quick.