Few random thoughts:
I have a hard time believing the Horizon would be looking at adding Denver or Omaha. I also have a hard time believing Denver or Omaha would be interested in the kind of travel the Horizon would require.
IPFW and/or IUPUI make the most sense.
With the addition of UND, the Summit is at 11. We could lose 1 or even 2 and be OK. It was only a couple years ago we survived at 7. Losing up to 2 teams wouldn't be great, but we wouldn't be on the verge of imploding.