Bluetooth HID access would be awesome, because that'd let people use the Adafruit board to create custom keypads (or it'd make for a really easily paired add-on if you made the pendant).
At the bare minimum, I'd love to have: up/down/front/back/right/left. Having red/green button equivalents would be great, and in an ideal world, the "set xyz home", "move to home/park/center", and set Z zero.
Basically having a tactile button for things that are behind menus but might be needed repeatedly during setup and test runs and such. If it's a job with multiple bit changes, it's a lot of "look at the bit, look at screen, why isn't the bit moving right, oh the mouse moved off the button (or my thumb is touching the screen in not quite the right spot), need to move another direction, look back at screen, look back at bit, try to watch the z of the bit while making sure I'm tapping the right spot without tactile feedback", etc. For a lot of people that's perhaps not a big deal, but personally, I get a lot of eye strain when doing that much back and forth in quick succession. Just being able to change and zero a new bit without needing to look away from the machine would be amazing. Having the green button available from a distance would make it easier when authorizing movement, as well as initializing a file when a laptop isn't right next to the Handibot.
Thank you for the info about the software/firmware updates as well!