Seasonal house, May-October, house itself made of aerated concrete block, electric convectors for heating. The floor needs to be replaced, as the old one is rotten.
I would like to do so – on the sand to put reinforced film to prevent excessive moisture from the floor, then lay treated antiseptic, on top of lay vapor barrier to eliminate dust and a draft, then board edging, with further processing of stains or oil! Vapor barrier of solid material on the joists and immediate board edging, without gaps as in insulation.
Asking for an expert opinion.
Your idea seems viable, but you've forgotten the most important thing: the air vents on the diagonals. Without ventilation everything is doomed. The lower the floors to the ground, the more intense the ventilation should be.