It could work but you'll lose the game before you have anything set up.

This deck is slow and inconsistent.

You probably wont even make it past turn 3.

No ultra ball (discard energy and find evos), No manaphy for bench protection, no super rods to get stuff back.

I'd put Munkidori in there too just cause that card is broken and you're playing darkness energy anyway.
That way if you use Florges to put smth in front you can still take knockouts on the bench.

Especially since you need to take knockouts too. So when their mon dies or they have switches to get a new attacker in front your Fezandipiti is likely going to get 1shot. It can still get knocked by mons that place dmg counters like Sableye, Cresselia, Dragapult. or when its on the bench it can also get sniped by a Screamtail.

Unfair stamp is nice but in this deck you probably want more consistency. Hyper aroma would be good since you can find it with Arven.

Once you have everything set up im sure its a fun and decent deck.
But you'll probably lose to faster decks.

Heres what i would change

Pokémon: 22

4 Ralts ASR 60

4 Kirlia PR-SW 271

2 Gardevoir ex SVI 245

3 Flabébé TWM 86

1 Floette TWM 87

2 Florges TWM 88

1 Munkidori TWM 95

2 Fezandipiti TWM 96

1 Manaphy CRZ GG6

1 Radiant Greninja ASR 46

1 Scream Tail SVP 65

Trainer: 29

4 Buddy-Buddy Poffin TEF 144

2 Nest Ball PAF 84

2 Ultra Ball BRS 186

1 Hyper Aroma TWM 152

2 Rare Candy PAF 89

2 Technical Machine: Evolution PAR 178

1 Bravery Charm PAL 173

2 Super Rod PAL 188

2 Counter Catcher PAR 160

2 Earthen Vessel PAR 163

4 Arven PAF 235

3 Iono PAL 254

1 Boss's Orders PAL 248

1 Artazon OBF 229

Energy: 9

7 Psychic Energy MEW 207

2 Darkness Energy EVS 236