First of all, oil sounds like an inefficient mess. I wouldn't consider it.

In Thomas Hill's book Ultralight Boatbuilding, where he shows building boats of plywood, he uses epoxy/glass on the bottom for abrasion resistance. For the rest, he states very clearly- epoxy is for gluing things, paint is for painting things. He details multi-year abuse tests on marine plywood that have not failed, and says that Paint is all you need. He's not building stitch-and-glue, in general he's building lapstrake, so you'll have some necessity for fiberglass/epoxy fillets, but you will probably be fine painting everywhere else.

m