Pashuteh, The Sefardim, until very recent times, have taken more than one wife. As far as Askenazim, the Torah specifically recognizes Takanos Rabbonim, which Cheirim Rabbeinu Gershom (and some of the other concepts you mentioned) is one of.
Pashuteh, The Sefardim, until very recent times, have taken more than one wife. As far as Askenazim, the Torah specifically recognizes Takanos Rabbonim, which Cheirim Rabbeinu Gershom (and some of the other concepts you mentioned) is one of.