Thats a pretty silly example, gamesguy.
Hey, it happened. And man was I proud of my little armored car.
Also, at least one of the veterancy levels (preferably the first) needs to increase its damage. Its a offensive unit, not a damage soak. Hopefully AC will also be targeted by the "reduction in neccessary experience to level up"-buff all "mediocre" units soon will receive by Salan's grace
+5 vision and the 20% received accuracy bonus would be enough at vet 1 IMO. Its gun actually has 40 range, so if it got 40 sight, it could kite infantry. It would take a lot of micro, but its doable. The problem with halftrack armor, is it takes 50% more damage from AT guns, which means with that armor a single hit from a 57mm will kill your vetted AC. Changing armor types tend to have unintended consequences.
Something like this would work better I think:
Vet 1: +5 LOS, -20% received accuracy
Vet 2: +2.5 LOS, +2.5 range, +20% damage
Vet 3: +2.5 LOS, +2.5 range, -25% received damage, overdrive cooldown reduced to 45 seconds.
This way, at vet 1 you can sort've kite infantry the same way a cromwell can, at vet 2 you get more room for error when kiting plus extra damage to help you gain vet faster, and at vet 3 the AC has 45 range and 45 LOS meaning a well microed AC should not die to infantry. It also becomes more resistant to AT(but not overly so, 57mm still two shots it), and gains a overdrive bonus which essentially allows the AC to be on overdrive 3/4 the time its on the field.
I would personally pay for this vet, and it wouldn't be overpowered. At vet 3 the AC becomes a infantry harassing monster, but its counters will still kill it fairly easilly if you don't pay attention.