By way of thanks I offer pictures of this crazy job. I ended up having to run a hose into my house to soak the dryset quickerete. I don’t care what anyone says I’m not mixing cement in my house. The whole slab is supported on top of 2" floor insulation on top of a leveled bed of crusher dust.
Addition photos in comments
Neat approach to dealing with the clean out.
Glad you went with concrete, it really is the best answer. Even if it was imperfect, it’s would still be better than wood, since it’s not structural.