Bootstrapping landscape alphanumeric RPN

[sa-penguin]

Option A is a good start.
Using something like PhoneGap, you can create HTML-based screen layouts. For those demanding a particular keypad layout, this allows you to play with positions and customise.
It also allows you to do things you might not want in the real model, ie. custom keys (do you really want a touch screen on a physical calculator?).

Other benefits involve things that would be mighty hard to implement on a physical machine. Imagine pressing the function key - and suddenly, ALL main text on keys gets "swapped" with the secondary function text. [The only way I can think of doing this on a physical board requires backlighting LEDs, and sheets of Perspex acting as "optic pipes"]