Why was it changed? I think I remember stun rods not triggering reactions in UFO (miss, miss, step aside and die was pretty common..) Did melee not trigger reaction in TftD either? Can't remember that one..
If it didn't in TftD, that would be a case of "staying true to the original" (however unrealistic), and maybe global toggle would be warranted. I can't really think of a situation where weapon toggle really makes sense.