If I was to build a Fighting type mono team (I can use two pokemon that arent fighting type, as long as one has a fighting move) and the rules are these:
Level 100
Double Battle
No Legendaries
what advice would be given towards the two pokemon I should add?
Well, that's a bit tough...what's the rest of your team, anyway? Well, you'd probably want to add something with good defenses, probably an Explosion resist or something since most fighting types have suck defense nor the speed to take down an Exploder, so maybe something with Damp or maybe a good Steel type that can set up a Screen like Bronzong or something. I dunno; I really can't tell without knowing the rest of your team.
On a separate note, does Mew get Role Play? I had heard something to that effect somewhere but Serebii and the Smogon movedex aren't saying anything to support that.

