I know some of Artoon remained at First Studio, but the VAST majority are at Arzest. They should be the ones on any The Last Story project on Switch. Hell TLS was in Terra Battle which Arzest has some involvement with (mostly guest character designs by Naoto Ohshima and Manabu Kusunoki IIRC).
Looking at the credits the actual leads/staff from MMV on TLS seem pretty spread everywhere now. Most by far are actually at First Studio (and multiple people also worked on the Fate/Extella series, Soul Sacrifice, MH Stories, God Eater 3 and Daemon X Machina btw) but you'll find one or three others at Omega Force, NdCube, Mistwalker, Square Enix, Creek & River, Game Freak, Orca, Bandai Namco Studios, Capcom, Konami, Toy-Logic, Monolith Soft, Ubisoft Montreal (lol), Cyanide SA, Digital Works and yes Arzest (among others). It's important to keep in mind that while a good chunk of Artoon staff worked on TLS (many from Blue Dragon actually) basically just as many also came from Cavia and Feelplus too. It really was a group a effort.
It disappoints me that Konami doesn't look at the absence of a real FIFA game on Switch as an opportunity to convert millions of ppl to PES. There's an opportunity, but they either don't see it or don't believe it's worth it.
It's doubly weird when you consider a decade ago they had multiple teams on the IP so they could deliver SKUs tailored to about every platform: 360+PS3, PS2+PSP, DS, Wii and later on PSP+3DS. I always figured the lack of ports outside the 360/PS3/PS4/One quad (even when it arguably made sense like Vita or Switch) had more to do with not wanting to port FOX Engine after dissolving Kojipro and they've sort of confirmed that when they said they're dropping the engine for next gen. It's kinda crazy but maybe we'll see a Switch version alongside PS5/XSX instead if they use UE4 or something?