I'm not sure. I did spend a few minutes while bored out of my mind at work looking at stuff for the Fire 6 HD. Plenty of stuff came up at XDA, but I didn't look too far into the sections. I wonder if it might be too small?
I didn't even know about the Samsung Tab A (Germany for now) until I came home and was going through posts at Liliputing. It just came out a couple of weeks ago. I presume it has the same hackability as any other Samsung device. Not being a Samsung user, I can't say what that is.
Something else I saw at Liliputing, was a new dev board. They post them up every now and again, and they are basically Android motherboards so generic Android should run. The comments about the particular board I was looking at were strongly negative, so I didn't post a link. However, combine a dev board with a display that does fit (Xenarc?) and I would imagine you'd be good to go!
Another thing I thought of, was that rather than hacking up an existing Nav bezel thingie, why not make a mold of it and then work from the mock up? Or maybe some enterprising soul could make a mold of the JDM/AVO part, then adjust it's asymmetrical RHD layout to be more LHD friendly?
SC