I addressed this comment directly in the first post. Vet 5 should not be an all out win option. In which case just have a button unlock when it hits vet 5 that let's you win the game outright.
Alex, I don't feel it necessary to address your comments because you have not made reasonable arguments.
What do you mean? The Command Panther's mark target ability doesn't last as long and as far as we know only increases the damage taken by the tank by a marginal amount more than the Soviet version.
The C-Panthers biggest benefit is the sight bonus it gives to your tanks, but many people are discounting the fact you can only have 1, and it can't be everywhere all the time. As far as "OP"ness goes it's not at all, it's a Panther that doesn't scale like a regular one in exchange for the Aura it has.
At only 30 less fuel than the IS2 and in a fuel starved faction the C-Panther is fine cost wise, really the only thing it might possibly need is removal of the overclock ability which allows it to slip away and kite very easy.
EDIT: In addition to the accuracy being different; it also has a longer reload time.