If you're taliking about having a team in a market that just doesn't make sense then JAX is definately it. It's a large city (14th in the US), but a terrible location for a team considering that the Fins and Bucs have already locked up most of Florida's fan base.
However the 32-team system does work perfectly. The only way to subtract is to move a team somewhere else or add 8 more teams, thus creating a new division in each conference.
On that note there are several markets which could/should have an NFL team. LA of course, but also coming to mind are Las Vegas, Portland (Ore.), Omaha, Salt Lake City, Des Moines, Jackson (Miss.) and Oklahoma City. I wouldn't be oppossed to seeing a team in Honolulu although the travel logistics would be a nightmare.
I'd say Columbus, Ohio could handle a team although this could be similar to the JAX situation where most Ohioans (?) already support either the Bengals or Browns.
I also think that the NFL will have teams based out of Canada and Mexico within the next 10 or 20 years. It makes sense business-wise for them to capitalize on these markets.