I am big fan of epoxy laminates. Messy stuff, but playing with it for 50 years I know how to keep it clean.
Even when you have 50% of the wood gone and rest barely holding, you can soak the leftover with epoxy and add fiberglass on top of it.
Done right it will be stronger than original wood and mostly waterproof.
1 qt of fiberglass resin cost $16 at Home Depot.
I replaced most of wood under cabover on my Fleetwood Caribou.
The camper has skeleton aluminium frame, so I screw new 1x1.5 rails to it and then replace about 70 % of length of the cabover wood frame.
Turned out I was sleeping supported by 2 toothpicks, so I put solid 2x6 board under the nose.
