Vacu-forming will provide you a shell but no reall strength like the glass molded cone will. Also you'd still have to make the temporary canopy plug to fill in the gap.

A variation on the glass work from the past. The old Petit HobbyPoxy company EZ DOZ-IT method using a balloon. Make up the firm balsa plug for the gear opening as already suggested. Then get some long hotdog shaped party balloons, the ones that blow up to be about 4 inches round and 2 feet long. Blow one up and push it on over the nose of the model with the nose touching the end of the balloon. Let the air out as you push it over the nose of the model and keep going until the nose is trying to come out through the nozzle of the balloon. At that point cut the nozzle off and pull the balloon over the model so the nose is coated in rubber. Rub it down with some silicone type rubber and plastic creamy auto buff up restorative goop and wipe sort of dry. Now prep your glass layups and mix up the resin. Drool it all on the nose and then put on another balloon the same way you did the first but this time it goes on over the glass layup to act as a pressure jacket. Some of the same auto rubber and plastic detailer goop rubbed onto and the excess taken off will ensure the balloon doesn't stick.

For a glass layer of a nosecone like this that'll have to withstand a lot of impacts I'd suggest two layers of 2 oz woven cloth with a layer of 2 oz matt between. This will result in a layup that's between 1/32 and 1/16 thick. Obviously a bit extra cloth at the nose wouldn't hurt. If you watch your seam overlaps and avoid any voids at the joint it should come out with little if any lumps. And seams should be staggered to avoid a weak line. Overlapping the woven cloth is fine but avoid any overlaps or voids in the matt.

Do it right. That model looks like it's worth the extra effort. Nice find too!