We recently had a look at a Jeanneau 11.50 that was the same. I'd think you'd have decent success with a zip blade and a mini grinder (or possibly a dremel) to cut the glass around/over the bolts.. in this case it all stood proud of the bilge/hull.
It will make an unholy mess, though, and dust everywhere....
1984 Fast/Nicholson 345 "FastForward"
".. there is much you could do at sea with common sense.. and very little you could do without it.."
Capt G E Ericson (from "The Cruel Sea" by Nicholas Monsarrat)