I don't think Avon goes anywhere unless Brownsburg goes with them. They have a long-standing rivalry.
FC would make more sense. They're a geographical outlier in the HCC and at least would have shorter roadtrips with Marion County schools than going to Brownsburg and Zionsville. Franklin Township is exploding in population, though, and will likely be, enrollment-wise, on par with the larger MIC/HCC schools before long. They'd be one of the stronger teams in the MIC in the non-revenue sports.
I'd make a call to Tech, who honestly fits very well in the NCC everywhere except geography. However, IMO, they'd struggle to compete in the MIC in just about every team sport except basketball.