1st pick: Figure 1 (N800 FF w/ one row of keys)
To maximize the text entry experience, I'd impliment a hardware and software solution to be able to do the following - keys are pivotable (like a d-pad) and know if you pressed the center, right, left, top or bottom - with each "position" assigned a character/value. For the software side, I'd implement a version of the text entry software for the BB Pearl, that predicts what word your looking for (but better & more easily able to put in non-standard/dictionary words)

2nd pick: Figure 9 (phone shape with fold behind keyboards)
This looks like a very compact FF (good), but it also looks like it could be very thick (bad)

My 2 cents