The biggest issue with a Linux tablet, is you don't have a lot of tablet apps for Linux. Desktop apps don't translate to tablet usage that well. I found that out when I was using a Chromebook tablet, with the Linux mode add-in. Tried using things like openoffice, even firefox, and there were just too many issues (smaller tap targets, things like dragging your finger on a window selecting text (i.e., what a mouse would do) instead of scrolling like you would expect on a tablet of phone, etc).

So you are either running Linux with a web browser that has a tablet mode, and making sure all apps are web apps adapted for mobile or at least non-keyboard use. Or you re-invent Android. One thing that somewhat worked was Nokia's Maemo -- it used X11, but the defined UI toolkit and guidelines made everything uniform and touch-screen friendly. Not sure about how the successor projects look if they are what I remember from Maemo / Meego (so maybe Sailfish or Tizen, not sure how open these are though).