I don't think you would regret this augmentation to your current system at all Tim, and with your tool and skill sets, it should be a relatively easy addendum to the concrete floor system you have now...

I haven't had (or seen) a complaint of noteworthiness yet from anyone switching from concrete to wood, nor those that upgraded to their current slab system with wood...

Those of us with the luxury (and/or skill sets) to install wood floors (floating or fixed) thus far have all been rewarded with less Back and leg pain for our efforts. I would also note, that it is a great way to take an old, cracked or uneven concrete slab and more cost effectively improving it without removal of the original materials...I have seen or done this to Basements, Garages, and many other structures with slab floors. Where gravel is in place on contemporary systems, the use of wood over gravel (in my view) is a vast improvement both ergonomically and environmentally, to ever employing concrete.

For radiant heat systems, a simple layer of geocloth over the gravel layer, then sand or stone dust to hold the tube labyrinth is more than enough to facilitate all manner of tile, stone or related Hard Surface flooring material...even wood...Yet, because of the sand/dust embedment material still offers much greater cushioning than a monolithic slab system. It is usually much more cost effective as well (big picture) in the long run, and facilitate repairs/upgrades better than any monolithic system.

Regards,

j