Wiser system without zone valves?

[fuelmiser]

I have an oil fired sealed Y-plan system with a two zone Wiser system. All rads have wiser valves fitted. 

 The mid position valve has required replacement twice over the years, and I'd like to eliminate it altogether as a weak point in the system.

Given that the wiser rad valves are able to independantly close off the flow from the pump, and the hot water is only on for around 30 mins per day to heat the DHW tank, it think it's unnecessary to shut off the flow to the heating circuit when DHW is selected.

SO...I'm wondering... why why not replace the mid position valve with a tee, or just fix it in mid position,  and put a simpler zone valve in the DHW heating circuit? The microswitch in the zone valve could be used to control the pump so the pump starts after the valve has opened, to prevent noise. 

Any reason this won't work?