Alright, in the battle against Grimsley I'll send out Mr.Mojo against his Krookodile, but then bring it back and send out Ninja again.
Concerning soloing N, I just looked over all of the challenges and Mr.Mojo can solo N in Nimbasa with no conflicts, however he cannot battle with N in Nacrene City nor Chargestone Cave do to Rebel the Drillbur's restrictions. I'll just make up for it by knocking out 3 of N's Pokemon the next possible battle with N (1 for Chargestone, 1 for Nacrene, and 1 for whatever battle that I'm currently in).
Thanks for the help, I really appreciate it!