I have been following this and wasn't sure if I wanted to wade in but I decided to share my experience. I have built a lot of Fuselage Frame boats and reskinned quite a few.

I started out using BLO on my frames before I knew it would cause my boats to be eaten alive. Funny thing is after years of use and abuse when I reskinned I have yet to ever see a boat that had any damage related to mold/mildew. I have not even seen one that had anything more than some minor staining on the wood. This is based on several boats, several years old, not just one. My experience makes me think that the horror stories of BLO might be slightly exaggerated.

Of course I have never worked on one that was skinned in clear plastic either and I have a feeling that UV is an issue here. I did not see the OP say what type of wood was used and I suspect that could play into it too.

Since I hate oiling frames I have tried other things. In my classes we apply water based poly because it dries fast and it seems to hold up well. On my personal boats I have skinned bare wood frames and except for the wood turning gray I can't see any real difference once torn apart. I should should point out that I build with Baltic Birch plywood and I used Western Red Cedar for the stringers but my first ones were 'Marine Grade' fir plywood but same results on tear down.

I know epoxy is very popular and needed in a strip build but it is not needed in a Fuselage Frame. Instead, build with good materials and store the boat so it can dry out and stay dry. These boats are simple to build and the method has been around long enough to be a proven method, I see no reason to complicate it. From what I have seen as long as they can dry out they will last many, many years.