Creative idea. But a lot of work to square up all the stanchions' bolt holes?
We've got different boats, but my stanchion bolts also go through the deck frp and are secured by a nut from inside. For one person maintenance, I've had success by locking vice-grips on the head of the bolt. Then with a socket wrench on the nut from underneath, the bolt might turn a 1/4 rotation or so before the vice grips come up against something firm. The toe rail in my case. Then nut tightening can continue without the bolt turning anymore. A picture of the two bolt heads of my stanchion bases is attached. It is a precise trick to get the vice-grips firmly on my bolt heads.
Another idea might be to purchase 1/4" allen head bolts. These have a nice straight barrel head for vice grips to lock on to. Or maybe the allen wrench itself will seat snuggly enough to also wedge up against a firm part of the stanchion base.
I'm not advocating this as your "solution". Just the first thing that came to my mind as another alternative.
