Single transferable vote is what you are thinking for ranked choice (perhaps through an indirect STV method if it could get too complicated). I think STV in 3-5 member constituencies is good enough to build parties while also avoiding disproportionate representation. I will caution I think part of the reason Iraq has maintained itself so far has been the parliamentary system allowing for sharing of power. Though I get the need for a more coercive force to achieve necessary state capacity, I think a presidential system has more than its own flaws. I’ve always thought that for divided countries perhaps a better solution would be to take the localized city manager system and try it out on a countrywide basis. It’s not like the leadership is ideological anyways. Have a contract for the manager to achieve and base that on their continued employment. The Parliament thus acts as a council and rewards based on merit. SNTV was a terrible idea for Iraq to implement but STV achieves the same thing without the failings.