Hmm, maybe I've missed something, but it seems that you still have to create a new instance of the vanilla bucket for the universal bucket to deal with, with your own right-click functionality implemented so that you can pick up forge fluids ... Here's what I've got:
https://pastebin.com/r6p37jdc
I can't right click and pick up water. It just seems wrong to implement another bucket item for the "empty bucket" mechanics, but it seems like the universal bucket doesn't do this? This is from the onItemRightClick of the universal bucket: https://pastebin.com/zKy2KwFJ
"empty bucket shouldn't exist, do nothing since it should be handled by the bucket event"
What? This *is* the bucket. If it doesn't handle empty-bucket actions, then I've got to have two items (one empty, one for everything else) and implement the onItemRightClick of the empty bucket since the universal bucket can't handle it and the vanilla bucket has no idea about forge fluid handling.