Y'all are totally fine to post your lists, for future reference. I like to see themSo, understanding that both of you are experienced Vespiquen players, I will take your word that 28 Pokémon is the "sweet spot". In my tests though, I've found this list to work quite well. After removing the Field Blower for another Shaymin EX (which I believe I would prefer to have), I think that this has a fair matchup against most decks (the Ghetsis is the major difference, it can disrupt a lot of decks and give myself time to set up). I will test the Alolan Muk anyways just to see how it does, but I think that @GekkisaiDaiNi brought up the major flaw with Alolan Muk as it is difficult to set up with only a 1-1 line. Let me know what you both think, thanks!
Pokémon*27
Zorua*4 DEX
Zoroark GX*3 SHL
Zoroark*1 BKT
Combee*4 AOR
Vespiquen*4 AOR
Shaymin EX*3 ROS
Tapu Lele GX*1 GRI
Unown*4 AOR
Exeggecute*2 PLF
Oricorio*1 GRI
Trainer*29
Prof. Juniper*3 BLW
N*1 FCO
Colress*1 PLS
Guzma*1 BUS
Hex Maniac*1 AOR
Mallow*1 GRI
Ghetsis*1 PLF
Ultra Ball*4 SUM
VS Seeker*4 PHF
Dowsing Machine*1 PLS
Battle Compressor*3 PHF
Rescue Stretcher*1 GRI
Special Charge*2 STS
Choice Band*1 GRI
Float Stone*1 BKT
Sky Field*3 ROS
Energy*4
Double Colorless Energy*4 SUM
(@GekkisaiDaiNi, if you want me to remove this list just let me know, the Spoilers aren't working currently)
That list looks mostly good, but I'd cut the second Special Charge for a fourth Compressor. Really the only time I've wanted more than one Charge is against Trev, and they lock you out of it anyways. Plus you have Dowsing Machine worst case scenario. I prefer the 2/2 split of Zoroark to 3/1 but I can see the advantages. 27 Pokémon works, but I feel like damage is more consistent with 28. Plus I personally have gotten alot of use out of the Oranguru. I'm really liking the inclusions of Ghetsis and Hex Maniac here as well. Have you thought about a second Guzma instead of Hex though? For consistency.