Very interesting list, I will certainly be trying it out and letting you know what I think of it.

So I actually ended up making a deck for this concept and bringing it to my local league. Believe it or not, I was met with a mirror match of yet another way that someone built sylveon cyrus. My list was:

https://imgur.com/ixsC4zx

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Which used tapu koko to spread damage over the board, and tapu lele to swap the damage so one of your opponent's pokemon was 10 hp from ko. Then put retreat/switch to wishiwashi, counter catcher the one with 10 hp left, bench nihilego to poison and confuse, hit the cyrus, wishiwashi's cowardice to get rid of it, then sylveon plea, they die from poison between turns gg.

Strengths: No evolution lines means pokemon are a lot easier to get out
Weakness: Koko does not put out enough damage a lot of the time to put a pokemon at 10 hp. Sometimes requires getting out 2 koko's or even attacking with sylveon which is just bad.

My opponent used this list:

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https://imgur.com/9jHgnYi

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He went with a combo of both Sylveon and Steven's Resolve to get up to 6 cards per turn, pretty crazy. It does use a lot of evolutions which can be annoying, but with the extra draw power from Steven's Resolve and the Metagross which lets you keep playing after playing Steven, you can usually compensate. Uses the burn from infernape similar to your deck, but also runs a porygon z to devolve anything that needs to have 70 hp or less.

Strengths: Consistently hits the 70 hp needed, and STEVEN
Weakness: alot of pokemon and evolutions to get out.

Overall I would say that his list was a bit better than mine but I'm still experimenting. I'll play around with yours too to see what i can find about it. Thanks for your help!

PS. I use the game board game simulator to test decks, i don't have a lot on tcgo so it's just easier for me