On the tin, would allow for conversion between different states of a material (ingots between blocks) as well as slightly different manufacturing processes for the same item (you may have one simpler recipe that takes more of a material, or a refined recipe that requires more work but returns the same product for less material)

Not related to allowed/blocked mod ids as those only switch between different json folders to load into the game while still having one recipe per json

Example of a needed usecase, a long planned paperclips material

I also plan on finally adding a TC alloy block, though I might rename the terrillium carbonic alloy to something more creative

This would fit nicely with the version updates, which will require changes to all recipies since item names changed in higher MC versions. This'll be a hair icky for extraMaterials. And how would one handle the GUI displaying these multiple recipes?

Either a sort of loopy arrow button to show multiple recipes, or automatically cycle through available ones in the bench (as well as multiple JEI entries)

I think the button is better, since there's less confusion. Will bug @Ooferine for a GUI update.

Crafting quantities would also fit nicely here, so that a Nuts item from the OCP could be crafted from two sticks, or nine Nuts items could be made from a Nuts Block (example)

Implemented in V21.1.0.