Something like a 2x4 on edge framework covered by tongue and groove flooring? Would this add a moisture problem? We do not want to walk on a concrete floor but desire the strength of the concrete. What if pex was in concrete for heating. Would this be a problem?

You can do it, but it may (I'm guessing) create extra work for the infloor heating. You are going to have a finished floor on top of the concrete correct? what does it matter what is directly below it?

Heat or condensation problems was what I was thinking and was asking if this could be a problem. I know in some direct wood flooring to concrete with pex heating has caused issues resulting in needing to be torn up and redone.