Encapsulating a cottage crawlspace built on bedrock
The "less complicated" solution is as typically found under mobile homes in cold climates, where the "skirt" if any is typically not insulated.

Pipe insulation and heat tape. Or these days, your better quality, less failures option (at least on the supply side) is an INTERNAL pipe heating cable. In either case, plenty of insulation on the outside of the pipes (both supply and waste) and preferably a "hard shell" of some kind to prevent animals from chewing at it.