I think that at this point you should stop thinking about your pokemon like "A team + Rotation" and start thinking about a pool of pokemon from which you choose the best six for each task. In my opinion, once you've taken the time and effort to have such an army of EV trained and high leveled pokemon, these distinctions make no sense anymore.
For episode 16, we will be fighting Adrienn, who's the fairy type gym leader. So, poison and steel types will be very useful against them. Crobat, Swalot, Magnezone and Mawile will definitely be helpful. Besides, I would expect them to have a (mega) Mawile, which is hard countered by fire, so Ninetales or Arcanine will be good too. I would pick your Ninetales over your Arcanine because I think it has a much better set, but that's up to you. The final pick can be whatever. Just don't bring any of your dark types since they won't be able to do much. I see Clefable a good option, as it will probably be able to set up in front of some bulky fairy type (Florges, Togekiss, another Clefable) and just sweep their entire team.
In general this is the way you should reason for every fight. Just look at your pokemon, look what you're fighting, and pick the best six pokemon for the job.
Why would you want to retire any of them after having trained them so much. Just keep them all. At this point, the only thing you need to do to keep them up to date is to level them 5 levels every episode, which is nothing compared to the effort you have already put in them. Besides, any of them may suddenly become useful at some point for some specific boss battle you might struggle with otherwise, so my advice is to keep them all and don't discard any of them.
In general you tend to have too many moves of the same type in a single pokemon, which is useally not too useful. For example, Gengar has both Shadow Ball and Hex, Swampert has both Earthquake and Mud Bomb, Pangoro has Hammer Arm and Sky Uppercut and Swalot and Crobat have 3 poison STABs each. Try to keep a single STAB of each type (maybe two if they give you something unique like Acid Spray in swalot) and look for either coverage or utility status moves. You should avoid having two moves that do practically the same thing, like Sludge Bomb and Sludge Wave in the same pokemon.