Multiple AC inputs protected by single MOV
Those diodes will have to be have a rather large single cycle surge rating or they will die to protect the MOV. 

Why do you think you need MOVs anyway, just make R3,R7 out of a series string of a few resistors so it will survive 3kV or so (Resistors have a voltage rating!) for 20us (Check the standards for required ratings), and use butch ZD and reverse polarity diodes.

Also, how is your circuit protection set up, if S1 and S2 are fed from different circuits I would worry about failure of one diode shunting power into unexpected places. How is the common neutral return done? 

I would either arrange to forgo the MOVs, or use one per circuit and make each isolated input have its own phase and neutral connections so as to avoid any risk of something unfortunate if someone hard of thinking wires the thing between two circuits having separate protection.