Weird system. 5 at large seats, and 16 seats from MMDs of 2 members each?
Yeah, it is, but it's not entirely dissimilar to the current setup.
Doesn't seem like there's much point in having partisan elections. It would be more of a one-party state than South Carolina in the 1930s.
Believe it or not, one of the current at-large seats was held by a Republican as recently as 2008 (albeit a socially liberal Republican, but a Republican nonetheless). There are also currently 2 Independents elected from the at-large seats. It's a possible that as a state, it could develop a unique party system, although with the Democratic Party still dominant.
Only because the four at-large seats are elected in staggered terms (two at a time) and assigned (i) the first, to the candidate receiving the most votes overall (regardless of party), i.e., always a Democrat and then (ii) the second, to the candidate receiving the most votes who is not a member of the largest party on the city council, i.e., always not a Democrat and historically a Republican but nowadays usually a liberal independent.
Before liberal independents started running for and winning the second seats, those seats were intended to be the designated Republican seats on the city council, and they literally cannot elect a Democrat (unless the politics of DC shift dramatically).
Anyway, I don't really see why DC would need to change its electoral system at all. The existing DC Council could just be the state legislature.