MultiSig is not easily to implement for now since we would have to taken into account the order of signing, although we did start discussing it, it is possible:
keybase://chat/grincoin#general/62800
Good suggestions. Mimblewimble-py would indeed be useful when building a Grin HW using micro-python, see this proposed bounty:
@renzokuken Perhaps add code in mimblewimble-py or just an example for reading and generating QR codes, then mimblewimble-py can be used while being air-gaped. That would be awesome, IMO!
I will add it to the wishlist above.