an upgrade to nested adresses would suffice too. I don't see why not. They're widely, if not everywhere, accepted.
Nested segwit would be a good upgrade and the only incompatibility issues will be with people running nodes that don't use multisig (which I think was before 2014).
I don't think it should be switched to bech32 based on how many people claimed to have "accidentally" hit the "bet" button when there used to be gambling on this site...