Yes, I am with you on this. I can be #3, or maybe #2.5. If you can find a picture of the tools I might be able to machine something.
I am going to fit an A568 to my car while trying to fix the 284. I expect it to take a year or so.
I found a reference to the detent mechanism being difficult. It shows a cover inside the bell housing that prys off to expose balls and springs that mate to grooves in the shift rail shafts. Keeping track of these is very important.
The input shaft seal is also an issue. It gets destroyed removing the retainer. It looks like a new retainer could be machined to hold a traditional seal.
Then the parts that need replaced, the syncro rings/blocker rings might be able to be built up with metal vacuum disposition or plating. Or just machine new ones.
I have to believe that some other Getrag transmission has close enough parts to work in the 284, but finding them would be a chore.
Anyways, I would love to share information going forward.