A more durable solution would be to have your mast re-anodized. There has been a previous discussion of this topic
which you might find helpful.
An internet search for mast anodizing will find several hits. Whether this would be for you is a question of access to a facility that can handle an object the size of your mast.
The durability of this approach would exceed that of your planned epoxy venture. The problem with the latter is that you will constantly (i.e. every few years) need to refinish the varnish or 2-part PU that you are using to protect the epoxy from UV.
Like paint, you will be adding a layer on your mast, which means adding weight. Given that the middle of the mast is more than 12' above the keel, any weight you add there will need to be offset by 4x that much in additional crew weight (assuming you can get the CG of the crew to balance on the rail and assuming a 45° angle of heel as the highest that you might try to recover from by hiking).
Other than those, I can't think of any other problems with clear finishes for the mast.