Replace one radiator (TRV) with in-floor loop, which parts needed?

In the middle of a renovation I've discovered one of my radiators is unusable, would like to experiment with an in-floor loop for this room.

I have a Weil-McLain Aquabalance combi boiler, 6-zone system, with TRVs for each radiator, and I'm using a Taco infinitely variable pump--it's very much like this Siegenthaler system.

I believe that I can simply run the loop in place of the radiator with a few extra parts, and I'm hoping to be corrected .

A few questions:

I know that I'll need a three-way mixing valve to adjust the temperature, and I think the pump should supply the head I'll need. I think I still want a TRV? If I leave the loop open, e.g. just with the mixing valve, that loop will always be calling for heat. So the TRV, then a three-way mixing valve?

Secondly is the TRV just sticking up out of the floor? What kinds of controls do we use that can be embedded in walls or floors? I like the primitive no-electronics, no-fuss TRV style and I have wall dials for all the other radiators.

Thanks all, these forums have been very helpful in getting up and running.