The process that you are all referring to is called a full finish. A full finish is
Step 1: 2-3 layers of a low viscosity epoxy like West Systems 105/207
Step 2: 2-3 layers of a varnish/polyurethane of your choice.
Teak is a oily substrate and varnish or polyurethane
has a good UV lifespan, it has a poor adhesion lifespan. A low viscosity epoxy will adhere far better to teak than any other 2 part varnish product, ESPECIALLY with the oily substrate. The problem with Epoxy as everyone knows it sucks in UV environments. That is why you should coat with your choice of Varnish/ polyurethane to keep the epoxy away from degrading in UV light while the epoxy does its job holding to the teak.
If you think it is a bad idea, I would direct you to some of the best shipwrights in the business. Delta marine
that makes some of the nicest Yachts in the world does this exact process on all exposed wood on every yacht they complete. This is where I learned of this trick. Few people do it because its expensive, time consuming and everyone's first reaction is epoxy on teak.... no way. I have done exactly this for several of my sailboats and the last boat. 2 weeks to complete but only needed 20 minutes of maintenance
per year after that. It still looked great after 6 years. In my opinion, this is the only way to go.
The best part is, on small areas where the varnish was starting to flake, I sanded down to epoxy, acetone wipe and reapplied a new layer of varnish. Looked perfect. In any other scenario, that would have involved a full peel and sand and reapply of all new varnish.
I will agree, if you leave your boat for several years to sit and bake in the sun without care, you are asking for trouble, but if you keep up with this application, you will be redoing varnish every 10 years instead of every 3-4.