IIRC in the last 6 seasons IU is 6-11 vs. the B1G West; 2 of the 6 wins were vs. Illinois with the other 4 vs. Purdue under Hazell. Against the rest of the B1G West in that time period I believe IU has an even worse overall record than it does vs. the East's "Big 4" (thanks to IU's one win vs. MSU).
add to that IU's record in bowl games during that span, and the only real areas of success are vs. an (often weak IMO) OOC schedule and vs. Rutgers and Maryland (IU being 1 game above .500 against each of those 2 schools).
So merely switching IU from the East to the West wouldn't automatically assure a substantial improvement in its conference record, at least not based on its actual record from the past 6 seasons.
Unless, in switching, IU could be guaranteed that it could stop playing the East's "Big 4" every year AND it could still keep playing Rutgers and Maryland every year--which ain't gonna happen.