SFOS:
- It has a terminal to the underlying Linux.
- It supports keyboard (both TOHKBD or foldable full-sized bluetooth "Stowaway"/"Thinkoutside")
- It has SSH (and rsync)
It has all I need :-D

More seriously - well availability of some more advanced GUI or Office software would be a bonus.
But currently, the main drawback I see is that Ubuntu has more or less dropped the ball on "Ubuntu Touch" (and as this is still an ARM smartphone under the hood, libhybris running solution like "ubuntu touch" are mandatory).
So it's going to be difficult to bring Fedora/Ubuntu to this, SFOS seems the only way to get some "real" GNU/Linux.

Also chen rightfully said he wanted to keep the number of OSes options low, specially regarding OSes he doesn't use on smartphone and doesn't know well.

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On the other hand, if all you need is a pocketable device with desktop-linux experience on it :
have a look at project pyra.

It's designed to by a portable-gaming console, but it has Debian as a standard OS, should be supported by other ARM32 distros, and should start shipping in the near future.

That should be a solution if you need LibreOffice or KDevelop on a device that fit is a (large) pocket.