A couple of things here..
Adding glass/resin instead of the foam core while likely not to add that much weight, won't actually be any better than having a foam core. Buying 2 part foam and shaping it is not really a big deal at all.. Pretty easy.. Check out this guy.
https://www.boatworkstoday.com/videos/r ... er-part-1/ He has TONS of great content.
Also.... you may not actually have delamination. I just repaired an 86 boat, because I was sure I had the delamination issue. I drilled a bunch of holes and just could not get it to take any epoxy. What had actually happened is the early boats were built a little to light and the inner skin of the boat had actually split and broken. You might start this repair by cutting a hole suitable for an access hatch at or near the soft spot and inspecting the inside.
I repaired my boat by simply overlaying glass on the inside with the boat turned upside down. Worked perfect and now we have nice solid decks.
Before discovering this much easier method I cut of a portion of the skin on the starboard hull to figure out what was going on. My decks now have hydro turf to cover this quick-ish repair which I think looks great.