We should buff the shellmet then.
For example, faster digging underwater that stacks with the right enchantment.
Back on topic though, I do believe out of all these suggestions, the beaver one is the most troublesome one.
That needs tweaking to be useful for players.
If beavers are to be introduced and if they are to build and maintain dams upstream of rivers, then there needs to be massive changes to Minecraft for it to work. I don't want beavers destroying trees, not even tamed ones, but I do think there is a use for their talents in Minecraft.