It is a scenic train ride if OP can stay awake :)

OP will have had a restful night in a lie flat 763 seat :)

And, of course, a perfect cuppa with a biscuit :)

I've only done the train from London to Edinburgh, so can't comment on the scenery of the Manchester to Edinburgh route.
I agree the train is a good option, especially since it stops right at the Airport. But it is slower than a plane, and realistically, the earliest (direct) train is at 12:10 (although 10:10 might be doable, if a bit risky).

If the train ride is scenic, wouldn't the plane ride be scenic as well (assuming no cloud cover)? :)

No cloud cover? In the UK? :D

It certainly would if the view is clear but the view from the air is quite different. The train route from Manchester to York is pretty good, though I may be prejudiced by having grown up in the area. After that it is the same line as from London. One virtue of the train is that TPE give you a three hour grace period for a delayed flight if you are on a cheap(er) advance ticket.

Thanks again to everyone that has provided advice and ideas! Your willingness to help a stranger is amazing!

I did attempt OLCI this evening and as @JonNYC predicted, I received the same error message that I've been getting indicating no seats available. I did set up an EF free trial to alert me of any changes. I plan to call AA again tonight though not really expecting anything. Assuming that expectation holds, tomorrow's plan is:

• Get to DTW by 9:30AM
• Plan A: Magic happens and they fix it on the existing flight
• Plan B: Push for them to book me on BA via ORD
• Plan C is push for a FIM. (Won't say FIM just politely reiterate that I know it's within their power to re-book me in J on a different carrier) I tried to put the below list together of flights with J availability tomorrow from DTW that seemed reasonable.
• Plan D eventually accept Y if offered with solid compensation (Though I'm not really sure what to ask for above and beyond a full points refund?). I also understand that they don't have to do this and can just put me in Y with the fare difference...
• Worst Case for me - fly to MAN and either fly or train on my own dime and try to get reimbursed later. We are traveling with hiking gear and have a rather tight itinerary that needs us in our rental car by midday 23rd if at all possible... Would really like to get there on the planned day/time and avoid the hastle of another flight/train ride... Any other type of trip a train ride would be cool but it doesn't fit well into our current game plan

If I have FIM success (apologies if this excel formats poorly once I click post): <defective URL deleted>

A reference point. I had an AA award ticket XXX-DFW, and a separate BA award ticket DFW-LHR. Weather delays in XXX meant that we were seriously delayed at XXX and would not make the connection at DFW. At the Admirals Club I was told SOL as there were no award tickets available DFW to LHR for the next few weeks. I asked them to contact the One World Help Desk, which they did. Lo and behold they opened up two seats on the BA flight for the next day (which was the first connection that we could now make). Although we had award tickets we were booked into revenue tickets for the DFW to LHR portion and even got frequent flier miles for that sector. So, the message is that they are not dependent upon award seats to get you to the final destination if something happens out of your control.

One other point. I live in the US but come from the Glasgow/Edinburgh area. My advice is that if it comes down to it, take the EDI flight in Y rather than a J flight somewhere that requires a train or car connection. First a walk up train ticket will be very expensive. Second, you will be a lot more tired doing this rather than flying Y direct to EDI. I have done that exact route and while the train ride isn't bad, it makes for a very long and tiring day. Plus, you will then need a taxi to get to your rental car, if you are picking up at EDI airport.

If you can connect via LHR, and fly to EDI with a reasonable connection then go for it.

But ... I don't think there are good options from LHR to EDI. Generally the availability tomorrow morning is either zero or one seat. So ... while getting to LHR would normally be fine, its not a good solution here.

I have a bad feeling about this. I hope he doesn’t get stuck in Y. I see AA giving a face palm at the airport and best case he gets a refund in the miles between J and Y (best case as in AA’s best case).

I hope the OP proves me wrong!

I strongly suspect the agents at DTW will kick the can over to PHL to "fix" the problem. They'll say "we show you confirmed in business, you can get your boarding pass at the gate in PHL."
Not sure how long the connection is, but time obviously works against OP. Maybe PHL-MAN is the best option at that point, if there are even any seats left by then. Or maybe they could get OP on something like PHL-AMS-EDI, using KL on the second segment (I haven't checked timing or availability)

Further research reveals that the Edinburgh route goes up the West Coast line, I use the Middlesborough train hence my thoughts about York. It's probably still pretty scenic anyway, it would be hard to avoid scenery in those parts. Hopefully AA don't need the seats and OP gets to fly directly anyway.