I've already posted it in Houston, but I figured I'd network it here as well. I was thinking of a secondary rivalry between Orlando City and Houston Dynamo, due to our historical connection via the space program. After all, it is going to be years before Orlando will otherwise be part of a more natural geographic rivalry (Atlanta or Miami).
Houston-DC-Orlando, the "Southern States that Other Southern States Don't Think Are Southern States" Derby. I'd watch it lol
I'm not sure there is anything quite Southern about DC any more. Houston-Orlando might work, except that they will be in different conferences.