Here’s my dream alliance setup —
Every year, one week is scheduled as Alliance Week. Promo the crap out of it on all the partner networks. Let’s just say week 4 or whenever, but make it the same every year.
For Alliance Week, one conference hosts all home games vs the other two. Example, Pac12 schools all at home, with 6 B1G schools and 6 ACC schools on the road. Then the next year, you rotate who is the host conference. B1G hosts, with 7 Pac12 and 7 ACC schools on the road. Next year, ACC host and B1G and Pac12 are on the road.
While they don’t work completely evenly because of conference size differences, your school can expect 2 home and about 2 road games in a 6 year cycle. If you are not playing in the Alliance Week games that year, schedule someone else (each schools equivalent of TDS, etc.)
I would cut to 8 conference games personally, but it would only be one OOC game per school so they could keep it at 9 if the schools really wanted.
Maybe make some sort of conference wide trophy/bragging rights system somehow?
Iowa State @ 
Utah 
.
