Bear with me here. I'm thinking (as I usually do) of urban combat here.
The Po II isn't a fast tank- let's accept that. (There's an article, I think, covering it, but I'm too lazy and cold right now to go digging for it). That's fine. Let's still use one as the centerpiece of our formation. We'll back with with a pair of Zahns loaded with whatever battle armor you like- I'm a Fa Shih fan (and it helps that they can ride externally on all four vehicles!), but the Shin Long is a good choice as well- or, if you buy into the Capellans in 3145 having access to more... exotic... types, see if you can justify the old Elementals or something like that. Salamanders would be my top choice, but Capellans with ridiculous fire-suits is getting out of hand.
So, we need a fourth unit. I'm going with an Ontos LGR because I love LGRs, and this gives me the ability to hit hard at long range with one of my two slower tanks, providing cover (along with the Zahn's LRMs) for the Po to advance into range to make that autocannon hurt. While the two slower tanks keep the enemy busy- pinned by LGR fire and forced to react or die by the Po's advance, the Zahns can use their speed to move quickly down a side street- dealing with enemy forces along the way with the MML and flamers- and get to a position where they can easily dump off the infantry. At that point, use them as support for the battle armor's advance- now the enemy has a few SRMs from the tanks, whatever mess the battle armor showed up with, and- oh yeah, the other two tanks are still advancing and making life hell. That Po's cannon opens big holes in armor- just the thing the lighter weapons the infantry and Zahns are firing will need to start scoring crits on even the heaviest of targets.
In open-field combat, this won't work as well, because the Po is too easily disabled. But in tight quarters, this would work pretty nicely. Zahns don't work great as lone units, and neither do Po IIs, but together they make a pretty nice team in this setting. I'm sure others will disagree on the Ontos, but feel free to insert another long-range oriented vehicle of your choice if you wish. That's just the one that comes to mind immediately since when I think 'long range fire support tank' I almost always think of the LGR Ontos. ;)
Is it perfect? No, this could be blunted by motive crits, good planning, bad luck, etc.- but it also could be pretty heinous against an enemy who doesn't react well to being flanked.