Cave trees and "Grimwood"

What if there were cave trees that generated under y level 0 and gave you a new type of wood. They would give you "Grimwood" and would generate on a new block, "Grimmoss". Grimwood would be gray. Grimmoss would look much like Warped and Crimson Nylium, moss on top of stone. It would look like a mix of moss and Grimstone. The cave trees would generate in the new Grimstone caves. They would have Grimwood as the stem and moss as the leaves. This would be a source of moss which is unobtainable in survival Minecraft at the moment. I think that this would be a very good idea and would make it so you can actually survive underground without going to the surface.