I'd pick a Jackson over any at-gun at any given time.
Pshrecks are fine the way they are. They are expensive and the squad can't fire it without being at risk of being shot at by the targeted tank. Pshrecks alone won't kill your tank since a reversing tank is faster than an advancing squad.
Thats a Benefit. A drawback would be to say what its Tech cost is, what its fuel cost is, and what faction its in.
Pak vs USF is like giving Jackson slower speed, Better DPS, More surviability (because you can always recrew a Pak) and somewhere along the lines of 350 Penetration (arbitrary value to demonstrated 100% pen capability of the Pak vs US Armor) also dont forget AT Riflenades would need to also have close to that effective pen and be Vet 0 (and more reliable)
The Pak is more then fine for what it costs and how effective it is. Which is why they will get stolen EVERY chance someone gets.