Below are the kubel key stats in comparison to other early light vehicles. Figures in red highlight the balance problem with this unit.
Looking at those numbers in the order listed above there are several problems including:
Target size (10) is too small, which makes hitting kubel with an AT gun at far distance (accuracy .04 for zis) hard. You have basically 40% chance of hitting kubel. And getting closer doesn't improve your chances so much. You have to be right next to it to get a 60% chance of hitting it. This unit needs at least a 15 target size to make at guns effective against it.
Acceleration at 4.5 is the fastest that I know of in the game and only the OKW puma has this kind of acceleration. In comparison all other early light vehicles have around 2 acceleration (less than half). This is the main reason why the kubel can avoid counters effectively and get out of flanks so easily. This number need to be brought down to be inline with other light vehicles.
Sight at 50 is the same for all of those units but given the kubel is essentially a mobile mg it should not have that much sight. This enables it to go solo, hunting unsuspecting units and suppressing them before they know its there (infantry have 35 sight), and this is exactly whats happening now. Sight should be brought down to at least 35 like all mgs and even I encourage bringing down all support weapons sight to 30, so that they can never go solo and be effective like the maxim is so well know to be.
Damage at 17.4 near and 4.8 far is insane in this unit, and while one can argue that suppressed units take less damage so its not effective as it appears it has almost double the dps of an m3 at near range. Even with less armor the kubel can take on the m3 which requires teching and cost fuel. Damage or penetration need to be reduced on this vehicle.
Penetration is actually higher than the m3 which brings the question why a mobile mg has this kind of pentarion. If damage is left the same this figure needs to go down so that the kubel can't counter everything including its own counters like the m3 and dodge truck.
Looking at those stats and experiencing it in game, the kubel was tuned into a super unit that requires no teching and costs no fuel and can take on all early counters and get out of most flanks with ease. Its combination of acceleration, sight, damage, penetration, and the fact that it requires no setup time like all other mgs and suppresses units before the first burst is complete makes the kubel the perfect example of an over powered unit. I just wonder how long it will take relic to fix this mess. Judging by the last mess (katyusha) it might be soon hopefully.
edit: This unit requires a fuel cost to minimize spamming and or a performance reduction to make it function properly in the early game.