Our company SOP (which I believe in this case reflects Airbus SOP), is to leave the switch on, never touch it, and only turn A/SKID & NWS off for abnormals. If your outfit is turning it on and off, it is likely an unnecessary holdover from Boeing operations. We were overzealous and turned it on and off initially, then saw a rash of switch failures, then saw the light of returning to Airbus SOP.
If the rampers want to hookup a towbar, their neglecting to insert the bypass pin shall be at their own risk. Our outfit puts the bypass pin in along with the chocks the moment the aircraft parks at the gate.
[rant] At some point being overly redundant and extra careful can start to introduce more opportunities for errors and unimagined odd circumstances. If properly using the bypass pin isn't safe enough, then perhaps it is even "safer" to turn off the A/SKID NWS, the green/yellow ***** and the PTU, and maybe not even turn an engine until pushback is complete. Then just wait several months until an aircraft, upon disconnecting from the towbar, promplty rolls down the apron and down a ditch for lack of accumulator pressure.