Well, I think I'd have to have watched Skyland to get a good idea of what's going on. Reviews can only tell you so much. I'm also starting Jojo's Bizarre adventure, so I'll have to see if I can fit Skylands into my viewing time.
That said, I hate characters suddenly getting pushed to the sidelines in favour of those with special powers.

Since Seijuns are unable to fly, the crew should be useful as they have the ship, which is a vital method of transport/getaway vehicle.

As always, the easy path for upgrading Mahad is to give him the symbiont. He'll have power to rival (or maybe exceed, considering Oslo's fear)Lena, but she has more versatility and experience, which keeps her as the main character.

Cortes can apparently punch Brigs to death. I don't think there's many upgrades that can compensate for that, except maybe spiky armour. The 'upgraded Brig' excuse certainly falls flat for him.

As a general idea that won't happen, I used to read a series of Books called The Shapeshifter. It was basic X-men/Harry potter fare, but with telepaths, telekinetics and other psychic powers (and one shapeshifter). One of the interesting bits was that although the heroes were a group of powerful psychic children of mysterious origin(the COLAs), there were also other people who had their own powers despite not being COLAs.
This could be something that Skylands could benefit from. The humans would have weaker or limited psychic abilities, but their powers would work at night. Of course, they might not count as normal people any more.