Maybe just an idea here for Chris:
Brushless motors could be an option.
I don't know if you know odrives https://odriverobotics.com/
There's a discord channel with a lot of great minds: https://discordapp.com/channels/369667319280173067/369667319280173069
A v4 is currently in dev. It'll be single axis with a smaller form factor. Near motors drivers may be an option.
stepper motors is not a right direction for precision and speed for a arm robot ...
https://www.youtube.com/watch?v=zUy89MT_Rkk