Sadly, none of your statements about the su76 is true. Su76 has less penetration than stug and fights against, in general, better armoured opponents. It also can't "kite endlessly". It actually can't kite at all becouse in 99% of situations it can't shoot on the move. This is becouse su-76 is the only vehicle in game that has a 0 degree firing cone, which means it can't change its line of fire to hit a moving target if its rotation is decided by the path of movement. So while it is possible to draw a path that lets a su76 fire on the move at a moving tank that is close (becouse it is a big target degree wise), it is pretty much impossible to do that on max range.
And by none, do you mean all? Strange grasp of English you have there.
"SU76 has far superior range and penetration to the Stug." Okay maybe "far" is an exaggeration, but
1) Su76 has 60 range, Stug has 50 range.
2) Penetration values:
Su-76 (0/30/60) 200/190/180
Stug (0/25/50) 200/185/170
3) Speed: Can't be bothered, are you crazy Allied fanboys really going to claim that the Su76 doesn't have high acceleration/speed values?
4) You claim that Su76 "can't kite at all". I'm pretty sure at least a thousand players have proven you wrong. Or maybe you don't know what kiting is.
From urban dictionary: Basically a hit-and-run technique commonly used in games
With 60 range, you shoot first. Then you pull back, which is really easy to do using the reverse button/hotkey. Assuming it's not one of those maps where a small branch can mess up vehicle pathing, you can easily get 2 shots off without exposing yourself to counter-fire. In any case, most players will be too cautious to dive deep into your territory with a weakened vehicle because any reasonable SU player will have mines/Cons/Guards.
You can kite even with slow vehicles like the su85. Kiting is basically about using your superior range to force enemies to chase/commit to diving you. Even rank 500 players are doing reasonably well, so I find it preposterous that you don't understand this concept.
Your comment about "shooting on the move" is also pretty ridiculous and shows once again how you know nothing about the game. Given the 50% penalty for shooting on the move, most decent players will shoot, reverse, press "Stop" hotkey, and shoot again.