Would the Grabpack be a Darkner, an item, or both?
Would Huggy Wuggy, Mommy Long Legs, Boxy Boo, Catnap, Doey, Harley Sawyer, Yarnaby, and Lily Lovebraids be Lightners or Darkners?
Would the Smiling Critters, Nightmare Critters, Mini-Huggies, Ruined Critters, Swapimals, and Wrongside Outimals be Lightners or Darkners?
Would the Bigger Bodies be Lightners or Darkners?
Would the individual hands be Items, Darkners, or both?
likely be lighteners considering they're alive and stuff (albeit almost all of them are insane/been transformed)
Perhaps they'd be more similar to how they looked before... you know, Stuff happened, in a dark world
Though this is assuming you mean "Someone opened a dark fountain in playtime co" instead of "What if playtime co was a dark world"
1st option, not 2nd.
Item
Lightners, after all they were human once.
Probably lightners, I think all the toys were human once.
Dunno what those are
Could go either way
Id say the bigger bodies would be a mix of both. I would consider them being bosses since they have a ton of health and I think the hands would be items, maybe some type of key item since equipping it in battle probably wouldn't do anything, kind of like trying to feed someone a pipis.
But the hands all have different functions and are used to kill the bosses.
Would there be no way to do a Pacifist route? Would we have to Genoslides everyone like in game?
The Green hand is used to kill Catnap , the Conductive hand is used in an attempt to kill the Prototype , the Pressurized hand is used to kill Lily Lovebraids, the Flare hand is used against the Nightmare Critters and Ruined Critters as well as Doey .
Yeah no pacifist in Playtime Co. only passing fists
It's more like Neutral or Genocide I think.
There should definitely be a Weird Route where certain antagonists are able to be spared.
You join forces with the Prototype to torture and torment the toys for as long as your lifespan
I was thinking of it being the more goodish route, where Doey could be spared (could probably prevent Kissy Missy’s arm falling off, Yarnaby could be spared (potentially even join you), maybe Harley Sawyer could be spared? He does kind of come back in Chapter 5 though, so maybe it's unnecessary. Baba Chops could definitely be spared.
Spoilers for Poppy Playtime Chapter 4, and the ending of Chapter 5.
I've seen someone play the whole game so far so spoilers are in fact a non-issue for me.
It would be AWESOME if you tamed Yarnaby instead of murdering him though.
No Doey and Kissy Missy are definitely spareable.
Maybe Huggy Wuggy if you spared Kissy beforehand.
Canabalism
I meant spareable 
Basically I’m thinking…
Doey: Spareable if you don’t crush him with the grinder, and didn’t kill a single non-boss toy beforehand. Instead of killing you he’ll monologue like normal, but instead will cry and revert back to his normal form. If you talk to him, he’ll tell you he’ll be fine, and to move on. He’ll rejoin you later in the vents with Poppy and Kissy.
Kissy Missy: Stall out a few turns, and Poppy will call her off.
Pianosaurus: Find the secret Pianosaurus Easter egg. After the dance, they’ll join your party.
Huggy Wuggy: Only spareable in Chapter 5, and if you spared Kissy beforehand. Stall out for long enough, and Kissy will stop Huggy from attacking.
Lily Lovebraids: Only “spareable” if you complied with everything she asked you to do. If so, you won’t even battle her at the end. She’ll join you, realizing the Prototype won’t take her to a Better Place.
These are the ones that I think could be spareable. Not sure about others though.
Bro I think Doey was WAITING for that