Maybe a fundamental question is, does anyone have any yeys or nays about the choice of
either: extend payment_address with segwit addresses, meaning payment_address would be a "hybrid" or "dual content" structure which would be either a witness address or a non-witness address. this payment_address class then would support both bech32, and nonsegwit base58, addresses.
or: leave payment_address as it is, make a new witness_address class which is either hybrid/dualcontent, or bech32-only (and then what about p2sh segwit)
