It’ll be a month or two before I get a chance to play the game, are there plans to work on an in-game viability tier list, or has the removal of the majority of trainer battles obviated the need for one?
Yeah honestly this game doesn't really feel like one that could use a tier list, per say.
Even with "good" Pokemon there's very few required battles and the ones that are there are probably going to be about as dangerous. Nobles can even be done without battling
at all, though it's obviously more favorable to do a battle.
Meanwhile a tier list is kinda-sorta made with the idea that you're only catching what you need, but the way everything works in this game you'll be required to catch and use stuff anyway, so it's like...Kleavor is weak to water and you can send 6 pokemon at it every single time and you almost certainly had to capture a bunch of water types, so a good pokemon doesn't matter as much.
The math of it doesn't really matter, if that makes sense.
In Contrast something like BDSP, which also doesnt have a tier list going, even with the exp share issue, there's way s to play the game where that team composition can matter throughout the entire thing. From the boss battles to easily cleaning up the trainers as needed, and so on, and captures aren't required so you have those kind of considerations to make.