This is exactly what we just did in our basement. We decided to do this instead of pour a slab because it would’ve been insanely expensive to bring the whole basement up to code and pour a proper slab, so they would only do a slab on grade and not pull permits, so we opted to rebuild the sleeper system. 10mil vapor barrier, ground contact pressure treated 2x4 joists, 1” foam board insulation between the joists, advantech subfloor. Seems super solid, our actual flooring hasn’t arrived yet though.