I can't be bothered to write an entire full-lengthed answer right now, but I can give some advice:
1. Scarf Swampert seems like an interesting choice. However, I personally prefer Dracovish due to its sheer unstoppable-ness after it outspeed everything and spams Fishious Rend. Scarf Dracovish outspeed 252 Jolly Cinderace, so take it into consideration!
2. Flame Orb Pheromosa typically isn't conventional, but this is from a doubles VGC 2021 standpoint of view. I would personally prefer either specs or band or sash for sweeping capabilities.
3. If you are going to have volt switch on Tapu Koko, it ruins the point of electric seed. I would prefer life orb, specs or light clay as a screens setter, but I don't like electric seed unless you decide to not switch out with Koko.
4. Barreskwada should simply not have assault vest. Banded Barreskwada is much more preferred or life orb if you want versatility.
5. Maybe not Quick Claw, but Specs or damp rock would be much more viable.
6. Aegislash's spread could be questionable, as 128 def. 128 sp.def doesn't necessarily mean that you will mixed bulky offensive mon. You might want to aim for tanking sucker punch from cinderace, shadow ball from Gengar, etc.
They're just a few points to consider, and I hope I helped a bit.
