Its a simple (hopefully) rework and it goes like this
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Loads and fires a Gr. 39 high-explosive anti-tank round that immediately stuns the enemy vehicle crew. (Toggle skill)
-The Pak goes stationary after paying the munition cost and stays for an undefinite amount of time with the shell loaded, after the first shot is made the pak is mobile again, if the ability is toggled cancelled the pak is mobile again but the munition is not refunded.
A more drastic approach could increase the PaK sight by 5 if it realllly needs more raw power, after the first shot the sight buff is lost.
This way a Pak will act as a "stopping power" that coupled with a stug can be useful for late game rushes and enhances the OST defensive aspects
stug variant could be changed too, but i would prefer not because it gives some hunting potential as it is now, as a 1 shot timed ability