A lot of a Bowser/Fox teams strategies are going to be about working off one or the other's strengths, since they don't have many direct synergies. That being said, they do have a few moves that make pretty good set-ups for eachother as well as themselves. It's not much, but you really would have to make the most of these. Things like Fox's N-air, Bowser's Jab, etc...
The only character specific gimmick strategy I can think of is that when team-attack is on, Fox can reflect Bowser's Neutral-B without it damaging him to rack up a bit of extra damage if you space it correctly. It ain't much, but it's a little something atleast.
Other than that, I guess both characters could be pretty good at saving eachother offstage in case of emergency, though I doubt either will need it often enough. Fox's N-air and Bowser's Side-B or Up-B would both be pretty good at saving a teammate, but... Of course, if you're using Flying Slam, just be careful not to... Y'know, KO Fox.
But yeah, everyone else is pretty right about them struggling as team-mates... Still, that shouldn't put you off, they do cover a wide enough set of styles that they could work together. Though, notably, both are stronger when grounded, so keep that in mind.