The only interesting form I can see Nimbus in, would be a Capture the Nimbus game. That could make it interesting.
It would be a team-based game-mode. One Nimbus would be randomly flying around the map, both teams need to capture the Nimbus and bring it back to their base. Downside would be, unlike Capture the Flag where one caries the flag on their back and still retains all abilities, in capture the Nimbus, you would ride the Nimbus to your team base and you lose all your abilities for the duration of the flight, save for beam and ball attacks for self defense. This would stimulate team play, because team members would need to defend whoever is riding the Nimbus, since he can't use melee, but he CAN be melee'd.