I'm working on a skyblock pack, and would like to make Enderman available much earlier than I want players to be able to go into the Misty World, but as far as I can find, it's not possible to disable it currently due to the special handling of giving it only once. If it was in the enderman loottable I could disable it with LootTweaker, but it isn't, and there's no config for it currently either. As such, could this please be added as a config option, so that us pack devs can control access to the dimension a bit more.

 Added config parameter )

Of course it can be done ...
Can it wait until the next update or need it in the near future?

It's not hugely urgent, so can wait until the next update fine