I don't disagree, but that, in and of itself, is different than wanting the division winner to be crowned based on division games only.
As unfair as the schedule appears to be, I couldn't find one example where either Big Ten division champ, won the division because of crossover games strength or weakness. I am not saying it doesn't exist because I didn't check every schedule, just the top 2 teams and teams within 2 games. Just nothing that was clearly because of cross over games.
SEC has protected crossovers, Tennessee has to play Alabama every year, LSU gets Florida, Auburn gets Georgia. Then you have the deep seeded hatred games between Missouri and Arkansas, South Carolina and Texas A&M, Ole Miss and Vandy and Kentucky and Mississippi St. The rest of the other cross division teams they play every 6 years or so. Is it fair, probably not, but the teams that are historically good in that conference, Alabama, Tennessee, LSU, Auburn, Georgia, and Florida all play each other. Which is sort of like Wisconsin vs Michigan, Iowa vs Penn St, Nebraska vs Ohio St and Michigan St vs Northwestern.