[Belmont Resident]

We bought a camp years ago that had no basement just a crawl space with siding around it and vents in either end and you cover the whole thing with 2" insulation for the winter.
The first year my water pipe froze and it was because the heat tape failed.
I replaced the heat tape with new stuff and it has never failed since, sometimes the simple, least expensive fix is the best.
I would not recommend cutting holes in the floor. Two reasons, one fire hazard and second you will always have cold air coming up from the basement into the living area.
Honestly if you have the crawl space completely sealed from the outside elements like it appears then heat will transfer down to it through the floors.
The exception could be if temps get unusually cold as in below zero. That was when our pipes originally failed.
Good luck with it.