The M10 does not need to be BR4. It has mediocre armor, mediocre speed, an open top, and an abysmal turret rotation speed. The only thing it would have going for it is the 76mm gun, but it is at a BR where all the medium tanks have a 76mm gun anyway, and these vehicles completely outclass it in every other way. Even the M18, with it’s practically nonexistent armor, at least has amazing mobility and an actual decent turret rotation. To make the M10 actually balanced and viable, it needs to be lowered to a BR where the 76mm gun could be considered an advantage over medium tanks at the same BR.
As an alternative tank destroyer for BR4, the M36 Jackson should be added. It still has the same speed and armor, but the 90mm gun and the vastly improved turret rotation would make it much more suited to BR4. Ideally it would make sense for lightly armored tank destroyers with open tops to be at a lower BR than other tanks with similar firepower, to make them more balanced and actually have a reason to use them.