InFloor big red upgrade options?

Skypalace

I have an inFloor hydronic system, with 3 zones. One gas-fired supply system w/ master pump, each zone has one of the old InFloor big red combined pump/mixing valves, feeding a plastic manifold. The thermostats control the pump at each zone, with any zone on turning on the master master at the boiling. The big reds are getting flakey & noisy, and the local InFloor dealer says no spares or parts are available.

I received one bid which basically stripped everything out, and switched to mixing valves at each , which was to replace all the manifolds with brass manifolds, replace all the Big Reds with mixing valves, and move all controls and pumps to the boiler location. The bid was substantially higher than I was expecting/hoping for, but I'm not sure it's necessary to fully strip and gut and replace all parts of the system (other than boiler and infloor loops basically).

This certainly works, but it would seem that you should be able to replace each big red with a controlled mixing valve and local pump. Then it's able to keep the existing working manifolds (which have brass inlets/outlets) and overall control system.

Anything I'm missing here? Attached is a pic of one of the big reds with manifold etc. The manifold and attached is all fine (no leaks/issues, individual loop flow controls all work fine), supply/return is bottom left.

My thought was that on/+12v from thermostat would control a mixing valve (perhaps this part isn't even necessary, a constant valve may be fine as supply temp is well controlled within range by the boiler control) and would trip a relay to run a local pump that pushes mixed water (return from manifold mixed with supply) through the the manifold.

Recommendations/disrecommendations for contractors in the Seattle/Eastside area appreciated also.

Thanks,

Jim