> Physical keyboard combined with a touch screen [...] doesn’t make sense because it eats space you can’t reclaim.

True, at least for horis; though on a vertically-shaped handheld it might make some sense. A traditional slab with a tray-table compatible pogo-attachable keyboard (with wireless option built-in) would be optimal, e. g. a modern version of the piano from the Sharp PC-3000/-3100 or the Psion Series 5.

And ffs, please do include at least a TAB key!