You’ve got both the NFL and NBA playoff set-ups wrong. In the NFL, winning your division isn’t determined by division record, but by overall record. The Seahawks got in at 7-9 because the rest of their division blew even worse. As for them hosting the Saints, that’s no different than when an 83-win division winner gets HFA over a 93-win Wild Card if they face in the LCS. As for the NBA, winning your division only locks you into the top four (the best wild card can actually be the two-seed if they’re better than the other two division winners, and HFA is determined by overall record, regardless of whether it’s a wild card or a division winner who has it.
Yeah, the NBA used to give their top three seeds to division winners but that changed starting last season. For instance, the Atlanta Hawks finished second in their division to the Orlando Magic but still took the No. 3 seed. However, the Boston Celtics won their division but had a record worse than the Hawks and took the No. 4 seed.
I think instead of pro basketball and football, you may have been thinking of college basketball and football. Those are the only sports I can think of that determine conference champions/seed conference tournaments exclusively by conference record.
Decent idea. The one major problem I see with this is the fact that teams playing out-of-divison games could easily decide to rest players. Red Sox-Mariners in April could easily turn into Astros-Dimondbacks in September.