I think that would work except that the base game version requirements don't overlap. It looks like Subsurface supports up to (not including) v2.0 and ST requires 2.0+
Works fine for me. It would be interesting if you could only access the underground from the lowest level of subsurface but I don't know how doable that is.
I think this should be possible as long as the lowest level of a subsurface has a name. I'm doing a lot of base-level updates to make surface-linking/tracking easier, and as of now that's the only thing needed.
