Assuming the construction is glued plywood (most likely given the sail number), there shouldn't be any issue with epoxying the joints both inside and out. Apply a sheathing of epoxy which covers the totality of exposed wood is something I have seen but on reading more on the subject, sounds like a potential recipe for disaster if any water gets in (it stays trapped and rots the wood).
I'm also about to start work on a vintage Merlin hull and will invest the time to strip the varnish from both the outside and inside. More importantly, I am going to strip back the varnish from the glue joints to expose bare wood and then run a small seam of epoxy down the joint on both the outside and inside. I won't epoxy the whole plank.
I'll also have a bottle of penetrating glue (like ZAP CA) handy in case there are any fissures that need plugging before the epoxy seam is applied.
In order to reduce this labour of love a little, I am probably only going to do this for the seams of the planks in the floor (probably the first four on each side). I will also design some strengthening beams which will help to strengthen the floor where it is pounded by the crew and helm.
You should find that there isn't too much need to get into the hull during this process.
The planks will then be coated in a one pack varnish which will be tough and adequately good looking (I am going to sand the varnish smooth anyway so aesthetics will be compromised by that process).
Hope that viewpoint helps. If you are on Facebook, join the Merlin Rocket Revival Fleet group, they love this type of subject!