Well, there's several battlefield roles that I felt were left unfilled by the current equipment lineup, or were inadequately filled.
This is only my opinion, but it seemed that the current best tank the SAoY has, the Troll, doesn't offer enough firepower to adequately support Power Armor troops, so the Type 34 tank was made. The variants of the GPC were all created to fill specific roles left unfilled too. The Mobile Gun to replace the current car towed artillery in the SAoY's inventory, as well as to act as a fast moving tank destroyer for any M18 Hellcat fans. The SPAAG for anti-air purposes if there's no orbital or fighter support around. And the ICV version for moving supplies, ammunition and the ammunition hungry PA themselves should they feel like not flying everywhere and just want to sit.
Let's face it, even though they can fly, sometimes, they just want to clamber into an armored shell and sit after watching some of the most hardcore shit hit the fan, right? That's what it's there for.
Now, as for the Yusou, I've been very well aware of it since the very beginning of the Type 34 Armored GPC development. There are plans for the two to interact in roleplay in very interesting ways to entertain the players, and I've been eagerly waiting for the plot to get started for this too.
I'm not trying to shove any new, unrequested equipment onto Yamatai - that's why this will be a 5th Fleet exclusive trial production run only. And the hover versions will only arrive if the players like what they see so far too, because they're the ones that this is meant to ultimately cater to. I'm repeating myself but I can't stress it enough; for the time being, it's meant to be just for 5th Fleet to test out, but if it goes well with the players and any other onlookers, hover versions will be made which can be adopted more widely.
Just as you say Nash, the Legions are most likely to use the finalized, finished version, and any dedicated ground invasion forces in the SAoY that plan to recapture cities block by block would likely enjoy the supporting firepower they provide for Power Armor troops too.
I'm trying to better fill out the equipment present to allow for "Combined Arms" to take effect.