@EEngr:
It's crossed my mind before but there are design issues among which refuel gallery unusables that can otherwise be avoided when taking advantage of the wing dihedral to naturally drain these into the tanks.
Another one that springs to mind is that wingboxes aren't the most ideal interface environment from a structural complexity perspective. The wingbox clearance from the refuel coupling and its frangibility constraint (i.e. where the bowser drives off with the hose still attached) are a few such more concerns.
I appreciate that scissor lifts are a critical path item when refuelling but then again they're being paid to deliver a service - so they better make sure it's working! Also in bigger aircraft the clearance of the belly from the ground is above head hight so you'd need a ladder to connect the hose and I know what most operators would prefer the scissor lift over the ladder anytime given the option! I like your thinking though.
@aveng:
I purposely asked a general question to see what everyone considered as safest given that no regulations exist today that point to the exclusive use of either the left or right hand fuelling side. As de facto and Island-Flyer point out, it seems that experience and subjective risk assessment of each airline and/or handling agent (assuming the provisions for both left and right wing couplings exist) comes into play when selecting the fuelling side.
@de facto:
So fast forward to the 787 and imagine you're the last passenger that has boarded through the stairs as there was no available airbridge. Once you've sat yourself down you hear an announcement saying that refuelling is still in progress so keep your seat belts unfastened. Are the right side doors going to be armed? Otherwise the only stairs are on the left side and in case of a fire you'll have to pull some pretty stunts when getting off the aircraft.