Sylveon and Florges have similar special bulk, but I feel that Sylveon gets the nod ahead of Florges because it passes bigger Wishes and Pixilate gives it a stronger Fairy STAB in Hyper Voice:
-Wish
-Protect
-Hyper Voice
-Heal Bell
Nature: Bold
EVs: 252 HP/252 Def/4 SDef
Item: Leftovers
Ability: Pixilate
Knock Off is best used with Assault Vest Azumarill, as it's very bulky on the special end and still dishes out pain in its own way:
-Aqua Jet
-Play Rough
-Power-Up Punch
-Knock Off/Waterfall
Nature: Adamant
EVs: 16 HP/252 Atk/240 SDef
Item: Assault Vest
Ability: Huge Power
Consider Knock Off on Gliscor; in the event Azumarill goes down, Gliscor acts as backup.
I don't know if mixMence can do well this generation because of all the Fairies running around. Outside of Iron Tail and Earthquake, Salamence can't do much to Fairies at all. Really, the best it can do this generation is Dragon Dance, but Mega Charizard X and Dragonite do it better because the former's Tough Claws powers up its main moves (Flare Blitz, Dragon Claw, Outrage) while the latter has better setup opportunities thanks to Multiscale:
Charizard X:
-Dragon Dance
-Flare Blitz
-Dragon Claw/Outrage
-Earthquake/Roost
Nature: Adamant/Jolly
EVs: 252 Atk/4 Def/252 Spe
Item: Charizardite X
Ability: Blaze
Dragonite:
-Dragon Dance
-Outrage/Dragon Claw
-Extreme Speed
-Fire Punch/Thunder Punch/Earthquake
Nature: Adamant/Jolly
EVs: 4 HP/252 Atk/252 Spe
Item: Lum Berry/Leftovers/Weakness Policy
Ability: Multiscale
If you insist on keeping Salamence, change the nature and EV spread to Naive and 64 Atk/192 SAtk/252 Spe for a faster spread.
Given the fact that Genesect switches around a lot and Salamence (or Charizard or Dragonite if you choose to use them) are weak to Stealth Rock, a Rapid Spinner may be needed. Starmie can do that. I'd suggest Excadrill, but you'll have too many Steels:
-Hydro Pump/Surf
-Psyshock/Thunderbolt
-Ice Beam
-Rapid Spin
Nature: Timid
EVs: 252 SAtk/4 SDef/252 Spe
Item: Life Orb/Leftovers
Ability: Natural Cure
or
-Scald
-Rapid Spin
-Psyshock/Ice Beam/Thunderbolt
-Recover
Nature: Timid
EVs: 248 HP/32 Def/4 SAtk/224 Spe
Item: Leftovers
Ability: Natural Cure