Remember that time when I said to Cal that I was going to give my opinion on this battle? Behold.
First of all, if Cynthia's being downgraded then this is harder considering Erza'd get AP advantage. It should be less than 4x considering Pokémon's scaling tho, so it's still fair.
Let´s see how Erza fairs with Cynthia's team:
Spiritomb:
- Can drain Erza's stamina twice as fast with Pressure.
- Is intangible (sans the rock).
Roserade:
- Can weaken Flame Empress Armor and is resistant to Sea Empress and Lightning Empress Armors.
Togekiss:
- Probability Manipulation (flinching Erza whenever's possible).
Lucario:
- Resistance to Sword slashes.
- Resistance to Fairy Armor (?).
Milotic:
- Damage Reduction (of Lightning).
- Resistance to most of Erza's arsenal.
Garchomp (I suppose he can go Mega to match Tier):
More of the same.
Most of them have Stats Amps and Debuffs to turn the tides even, and with the load of hax they have, Erza's done for.
If Spiritomb fights first then he'll be able to tire Erza, even if he loses after she realizes that her target should be the rock and not the spirit, she'll have less energy to fight the rest of them. She can use Fairy Armor (if for some reason its type is Fairy because of the vague reasons FT has for everything) to ignore Spiritomb's resistance but that doesn't change the fact that she has to aim for the rock and not the fog. She still lacks NPI.
Roserade can just drain Erza's energy via Giga Drain and poison her. She has the option to lolnope almost everything Erza has.
If for some miracle Erza gets to Togekiss, that would be the end. With Togekiss' power Cynthia can just spam Air Slash and keep Erza at bay, damaging her and eventually winning.
The result might change slightly if Cynthia goes for another combination (if she's tied to 1v1 fights ofc), with Erza matching some of the Pokémon like Garchomp. But Lucario is a real problem sans for the Flame Empress Armor and it has enough versatility to put her down when helped by precognition.
Anyway, Cynthia should take this. Erza can't fight forever no matter how you depict her stamina when her opponents have this many options to put her down.
And I haven't said a thing about Hypnosis and Dream Eater refuelling Spiritomb.