In engineering class they taught us that the jacket water system must exclude all air to prevent corrosion. Kgood, your WAM system has continuous agitation with air in the circulating tank. Maybe it's not a problem with proper addatives in the cooling water?
So I built my first cooling system with a circulating tank to vent the high points on the engine, and return from the bottom of the tank to the water pump suction. The expansion tank was conventional, and close beside the circulating tank. The idea being to have the continuous venting, plus the expansion tank to assure all air is removed from the system.
When redesign was required (cooling system didn't cool) I removed the circulating tank, it was too heavy. Now I take extra effort to purge the air from the system before starting the engine,(lift tail, add more water etc) and plan to have expansion push the trapped air out of the highest point; the thermostat housing. After a few start-stop cycles, the air should be all gone.
Disadvantage? not as much reserve cooling water in case of a small leak.
I'm just in early ground running, so I wouldn't say my system is proven yet, but so far-so-good. trying to keep the weight down is a continuing challenge. Still, it's cause for review...