Setting a comparator output when the Metal Press is currently working on a recipe which has not reached the transformation point - would help controlling the speed of the item feed towards the press, be an additional way to prevent overfeeding the press AND one more way to be like "guys, look how cool and useful the probe connector is, these lil guys can do anything!"

Credits for the idea go to Vinny#5873:
https://discord.com/channels/270295681829306369/339127815666532352/889116669245546537

I'd like some specification on this:

The metal press can have multiple items in it at the same time. Is the comparator supposed to output 15 if there is an item before the piston and 0 otherwise?

I'm unsure if "multiple items" means "multiple recipes" or "a recipe that has multiple items as an input", but the answer is yes, regardless.

I did not consider if there can be multiple recipes with an unreached transformation point/before the piston.

If there can be, for the use case mentioned above (redstone controlling i.e. an extracting conveyor), it might be helpful for the redstone value to reflect the number of recipes currently in the pipeline.

I think the most important info would be "can the metal press accept more input at this time".

That info should be able to be derived from the output somehow, everything else would be fancy extra information that some rare players with customized configs could use to display utilization by switching on redstone lamps or something or show it on an OC screen.

I worry slightly about the amount of block updates this will cause, but I'm willing to give it a try.

Hm. Maybe before setting the output, it could do a check if there's already items lying on the input conveyor block suitable to craft a recipe. That way at least it only updates the redstone when it runs out of that.