I'm all for mer based os running...
but for gawds sake make it a rr. that way it doesn't become a nightmare in upkeep.
I love arm and all...
but if you have the serious hardware...use it.
Base it off Debian...
make it an rr ...
throw, mer into the mix,
and then you have a bloody unstoppable tank of a distro ..
clean, spartan and not top heavy?
antix is a good debian rr example.
absolutely fab.
runs on a bloody toaster..
old hardware or new hardware...
looks beautiful, runs beautiful...
I don't suggest making any distro that can't be applied to as many devices as possible...nor would I suggest a distro which has a lifespan of 6 months or 2 to 4 years tops...with nothing but headache along the way...
I suggest another way after seeing (pretty much) a decade of the same problems attempted to be solved using the same solutions over and over...with the same result.
Inevitably I believe that making mer or fremantle or hildon or diablo ...essentially a maem-esque distro properly laptop/tablet compatible is the way to transcend the limits of the initial devices they were built for...
which is what solution we should (and seem to ) be running toward.

I think that making things more complicated than necessary esp concerning onscreen keyboards...welllll...

I do think utilizing existing (very plentiful) brand model devices which are as open and ...um hm...receptive...to linux is important..
the nexus line is a good example.

in particular..some device brands appear to work well until looking under the hood and there is something ugly like broadcom wifi chip or some other component that doesn't play well.

As far as tablets go...
I would seriously suggest a convertible hybrid which has a keyboard.
It isn't that I'm biased to my fav. and I'm extolling it's virtues due to a brand loyalty.
If any other product did what my hybrid does and can do...I'd happily be saying the same of it...
but my fav became my fav because of everything it contained, how well it's internal bits got along with one another and how well it got along with linux distros compared to sooo many laptops, hybrids and tablets I have used in the last 2 decades...
I've used uncomfortable desktops, netbooks, clunky and sleek laptops, antiquated (now) umpc's, the early tablets, recent tablets too, with and without attempted physik keyboards ...and hybrids...hybrids with docks that have the keyboard, hybrids with docks that have the optical bay...etc...
best model I've used in my time is the toshiba portege m700 m750 and m780 (i7 is my latest and last model they made)...everything in the brute.
the stylus is nice...it's great to use it as a proper laptop..it's great to flip the screen around and use it as a pure tablet....it gets the job done..it works with just about every flavour of linux I have thrown at it..
I rarely use the optical drive ....if ever...
8 gb of ram,
a tb hard drive internally ...purely for easy casual storage...
and I have a second hard drive caddy for the optical bay which I pop in and out as the desire suits me to play with any of 4 or 5 hard drives with various distros ( I don't know how many I'm currently playing with...I've lost count..) I shove in and spark it up for...
So in all...
I think It would also be a contender device line I think...
they are plentiful and cheap enough...

But no matter what decisions are come to (if any are actually to materialize...) concerning the next steps with distros and such...
I do hope sanity is a primary ingredient when considering the end result and what legacy it will have...if any...