Is it sustainable to have fanmade addons on a long term cobblemon world?

So I downloaded cobblemon recently and am aware of all the amazing addons to the mod that the community have made, and they look brilliant. One question i have however is what happens if I install an addon that adds an item not in the mod yet, then a later update adds that addon item properly? Like would there now be 2 versions of the same item in my world and would all instances of the addon version of the item disappear when I uninstall the addon? Same with Pokemon, if I catch mons that arent in the proper mod yet and uninstall the addon when they are, would the addon versions of the mon disappear or somehow convert to the official version of the mon. I love the addons almost as much as the main mod itself but am doubtful that its practical or sustainable for a long term World