In today's dev hangout starting around 21:30 (https://www.youtube.com/watch?v=PzfC_KKSkNc) during a discussion on riot quest combat solos...
Hungerford: "...but when the pig/pyg tank comes out, we still haven't gotten the concept art for pig/pyg tank, i can't wait for people to get their hands on pig/pyg tanks, i want people to see--i want to see troll armies--and some minions, that have like, 5 or 6 pig/pyg tanks rolling around, just causing havoc."
From the phrasing it sounds like he means pygs which makes a large based tank more logical, but it also sounds like they're a minion+trollblood partisan solo. In any case, I am totally converting some farrow tankettes. A Sturm and Drang double thresher+tankspam armored column list is in our future (I just hope it's good).
So on dev chat today, they confirmed this has 2 sets of rules in WM- a character version with the 2 pygs in, and a non-character version with closed hatches (much like McKay and railless interceptors).
It will be a minion model with partisan trollbloods, so yes, you can model it as a pig tank!
At present, they’re expected to be FA:2, but they said they’ve considered 3 or even 4, so I guess we’ll find out at release.