Here's where you lost me. The advanced residencies have decided that a preliminary or transitional year is necessary. If they didn't feel that way, these wouldn't be required in the first place. There are a host of reasons for this, ranging from the notion that it's important to be a generalist first before specializing, to having experience managing patients on your own, etc. I think most agree that residents get "shaped" a great deal during their intern year, and so the advanced paths believe them an absolute necessity. So you really can't say, "well the OP's terminal job won't require these tasks, so let's just cast aside this whole year for him, because his needs come first". That's not fair to the other thousands of folks who have to suffer through prelim years each year, and it's really not a reasonable accommodation. It's drastically changing the path to the specialty, taking away the year which many believe is where most residents really learn to be a doctor.
Why is a prelim year required before a PM&R residency? It's a really good question. Perhaps it's because it's "necessary" -- i.e. you couldn't possibly be a good PM&R physician without it. Or, perhaps it's simply because that's the way it is. Because, in the distant past, everyone did a rotating internship and then often switched programs into a residency. But, somewhere along the line some fields created categorical tracks, yet others maintained the separate intern year.
ED used to be a internship, followed by an ED residency from PGY2 to 4. Now it's a PGY1-3 categorical track (for most programs). Is that "fair" to the first people who had to do 4 years of training? Probably not, but it changed anyway.
Endocrinology is a subspecialty of internal medicine -- you need to do 3 years of IM first, and then 2 years of endocrine. Neurology is a stand alone advanced program -- 1 prelim IM year, followed by 4 years of neuro. Why is that? Why don't those interested in endocrine start in their PGY-2, or why isn't neurology a subspecialty of IM? The answer is probably "because that's the way it was set up many years ago by the people who decided these things".
So, my point is simply this: "we" might need to look at how training is structured. Perhaps a prelim year is a necessary part of PM&R training. Honestly, I have no idea. I'm not a PM&R doc, nor do I know very much about what they do. But maybe it isn't. Maybe it's just a left over remnant of a bygone era. And if it isn't, maybe PM&R could be a PGY-1 match, for everyone. I agree that a special exception should NOT be made for this one guy. Either it's restructured for everyone, or not.
I think your mindset of what is necessary would change if we made it closer to home. So look at it this way. What if someone for some honest reason couldn't do your 3 year IM residency program, but was sure he could do it for 2 years, so he wanted to just skip the first year, do the two senior years, and go off into some low impact subspecialty. I suspect you would not be taking the whole "let's focus on the needs of this guy, rather than the needs of the program" point of view. You would say "now way, this isn't a reasonable accommodation". It's really the same with advanced specialties. They have already streamlined the categorical portions of their residencies because folks come in having been "broken in" as an intern someplace. You can't skip that, any more than you can skip the first year of a categorical IM path without dramatically altering the training.
Let's look at IM. I don't think your example works though, since I have trouble imagining someone who would have the skills to start as a PGY-2 without doing a PGY-1 first [although perhaps someone who did an FM PGY-1 first, but that gets into politics, and the ABIM not giving credit for FM rotations]
Let's use the example of a student with a disability which makes them unable to do procedures, and perhaps makes it more difficult for them to work on the inpatient wards. But, they perhaps will do fine in the outpatient arena. The OP might fit that description -- outpatient clinics are usually on one floor, the patients come to you, no one is putting central lines in clinic patients, etc.
It's a really good question without a clear answer. The way my residency is arranged, I could not accomodate that. Again, this is a job that I am hiring people to do. Some parts of the job may be directly applicable to your future career. Other parts are not. Residents cannot say: "I'm not going to be a heme/onc doc, so I don't want to do the Heme/Onc inpatient rotation". My residency is a mixture of inpatient and outpatient experiences. That's the job, and is included in my essential standards.
But, nothing stops a program from trying to create a position that is mostly outpatient, with inpatient experience being less "hands on". The ABIM doesn't have clear standards on this, although the new milestones project does try to get at this somewhat. Still, it could be done.
Unless we feel that all IM physicians, regardless of their ultimate practice, need to be skilled in direct inpatient care. And that's the interesting question, to which there really isn't an answer.
And it's a slippery slope. Forget about disabilities. Let's think about someone who is interested in Endocrine. They want to be an outpatient endocrine doc. It would be possible to create a residency in Endocrine starting in the PGY-1. It would be mostly outpatient. You would become expert in diabetes / thyroid / etc management. You would learn how to manage DKA and thyroid storm by consulting on patients managed by hospitalists. You would never rotate on a Heme/Onc service, but you would consult on their patients when needed. An Endocrine fellowship currently follows an IM residency because the ABIM says so.
Is this a good idea? I don't know. I would like to think that what makes physicians think so well about medical problems is not only their in depth knowledge of their specific field, but their broad training in other fields and general medicine. So, I think a direct endocrine pathway would lose something vital and important. But we could certainly shave time off training with a change like this, which would save billions of dollars (or allow the training of more residents). And maybe trainees coming out of a direct pathway like this would be perfectly well trained. Perhaps I'm a dinosaur. [If so, at least I'm a dinosaur that uses social media]