Your whole argument is fair except this deviation. When a team like Marshal schedules nobody and beats up on nobodies, then loses to Akron (Leftwich or no Leftwich or injured Leftwich, no excuse) they do not deserve to be considered for a National Championship, regardless of record.
Okay, here's my update: the weaker conference teams have to go undefeated to get a potential wildcard invite to the Elite Eight... TCU and Marshall this year wouldn't qualify, but Marshall in 2001 would... and as long as there are no other worthier teams (like Texas this year. It hurt me to not include them in my top 8. I guess I could bump Boise St since they lost that one to Arkansas, heh-heh.)