You can create update package using rebar3 grisp pack and serve them with an https server or use grisp.io to manage software versions and update the board.
About the hardware, we are currently working on GRiSP Nano, that is a lot smaller, but we are not yet to the point we could do A/B software update, in fact we are still fighting to get Erlang running on it with only 16 MB of memory.