As Sloop is indicating above, there is a large difference between a wood boat that has a few layers of glass (an awful idea) and a wood boat that has a glass hull essentially built around it, using it as the form. If anything, a boat done this way LIFTS the waterline because there is no longer water weight in the wood. The hull, after this kind of process, provides shape and the basic structure. This used to be done on workboats all the time. I have a good friend who had it done to his '65 Pacemaker which is now really a glass boat except for the topsides and Awlgripped and v-grooved planking, which look like a mint-condition classic. A guy I used to have my clamboat next to, had his 1918 40' Cat boat/clamboat done like this. It worked out very nicely. Getting rid of that leaky garboard seam is always a good thing.
I still wonder why you'd do it when it's far easier (and hence cheaper) on most boats to simply replace the original planking, gluing/splining the seams if you like, and keep sailing.
The drying out part can't be over-emphasized. Unless you're oven-baking the entire boat, it can take years for the hull to dry out to an extent that you can guarantee there's no lingering damp in the timbers that will lead to unseen rot later on down the road.
To shave down and refasten the original planking, waterproof, cold mold over the top and then glass over that just seems madness to me and asking for issues later on, given that no boat stays perfectly dry and and a wooden boat (especially a large wooden boat) is designed to flex with the seas - not transmit new stresses into the original deck/cabin structure.
Sure, it'd be strong, and if well maintained could last a long time, but having seen what can happen to glassed-over double-diagonal hulls I don't think for a moment it's a magic cure-all for an old timber boat.
(Case in point: On one boat I'm familiar with, water got in around the port-side chainplates, ran between the skins and came out just above the saloon floor level about 6 feet aft! It was the most bizarre sight seeing water trickling out of the hull and flowing across the cabin floor. To discover the source meant tearing out both cabin furniture and the inner skin from the leak point forward, repairing the rotten outer skin from the inside of the boat, then patching the waterproof liner and the inner skin as you went.
Another, more shipwright-friendly case involved a section of fibreglass sheathing near the bow simply dropping off the outside of the hull during a race after water got between the 'glass and the outer skin. At least that one could be fixed from outside..