Oil, I am not sure I would do that. I think it would make the blade play duller and less crisp. And I don't think it would protect the wood from things that can damage it. And it would make the wood a little heavier.
Sealant....that is a choice. It isn't necessary. But it would protect the wood from the water in the water based glues. It would protect the top ply from being damaged when you remove the rubber to change them.
If you put a very thin layer of a good sealant, it will protect the wood and not change the playing characteristics in a detrimental way. But you would not want to put a thick layer of sealant on. That would change the playing characteristics more than most people would want.