Gotcha. I think Carmel is the elephant in the room and the team that most likely gets left out of conference expansion. I don't know if I would go as far as saying that schools are "ducking them" but their dominance in the country club sports would give me pause as an administrator. There literally is NO PATH to a conference championship in nearly a half dozen sports if you add Carmel to the mix. Plus they don't seem to travel nearly as well as I had originally thought and as much as you'd expect from a school with an enrollment of 5400+.
Avon is the next most interesting one to me as they are bottom feeders (at least the bottom half of the HCC) in nearly every sport and a chance to the MIC or this "Super Conference" you suggest would do them a ton of good as long as Carmel is not a part. I am not sure why the loyalty to Brownsburg as those corporations seem to be heading in opposite directions. Brownsburg is at the height of its athletic prowess right now in multiple sports and appears to just be getting started.
I think any administrator/athletic director doing its due diligence has to take a look at the future. That future, in terms of the south side is Whiteland. In terms of the east side, its New Pal. Westfield to the north and perhaps Plainfield to the west. The Marion County schools (PM, DC, SP) add no real value in terms of revenue or competitiveness across the board in my opinion.
Center Grove would dominate that potential conference in 15+ sports.