So what's wrong with:
1. Illinois State? It is older than any Big Ten school except Michigan, Northwestern, or Indiana. It's even older than Illinois by about five years.
Academics and its an old normal school/teachers college and is not a very large research institution like all the Big 10 members. Its also small, unlike the Big 10 and is not a flagship university.
2: Indiana State? It is older than Purdue.
Academics, an old normal school and see Illinois State, only academics is even weaker than Illinois State.
3: Illinois-Chicago? It is home to the second largest (and only one in the state) medical school. In addition, it's already part of the Big Ten Academic Consortium (Alongside the Univerisity of Chicago)
Its in the CIC likely because of an attachment to UIUC (the flagship). They don't get an idependent vote as their vote is combined with UIUC. If they didn't have UI's medical school they wouldn't be in it. Also, its academics is not on par with a Big 10 school.
4: IUPUI? It is home to Indiana's Medical and Law Schools, and Purdue's engineering school and the household pets program of Purdue's vetranary school.
It might have those IU professional and graduate schools but its really not IUPUI. Its really IU. Its a commuter school and its academics is not on par with Big 10 schools. Commuter schools are not the characterics of Big 10 schools, save U Minnesota, but thats the only flagship in Minnesota.
5: Wayne State? It is home the the nation's largest medical school. And if having one's regents elected statewide doesn't mean a statewide purpose, I don't know what does.
It have those Board of Governors elected statewide but unless you go to Wayne State, no one cares or pays attention, especially in Western Michigan and the UP. Its called a Metropolitan Research University like UIC but there are no Metropolitan Research Universities in the Big 10. Its academics is not on par with the Big 10 schools. There is no support for Wayne State anyplace outside of Wayne County as far as their sports. People in Grand Rapids, Kalamazoo, the Upper Peninsula, and Traverse City don't care about their sports.
6: The Dakota Schools? They after all are state flagships.
These are flagships, but they are the among the weakest flagships academically in the nation, saver the University of Alaska at Fairbanks. USD, UND and SDSU may be on par with Montana, Wyoming and Idaho, and NDSU is more on par with Montana State and UAF. But they would be worse than Illinois State and Southern Illinois and BGSU, and those are old normal schools/regional teachers colleges. Also, market is tiny in the Dakotas. Tell you what, I will ask some Michigan and Michigan State fans today about these schools and see what they say. It will give them a good laugh.