And strip OKW of their best counter to tank destroyer and medium spam? I'd rather not. The current Jagdpanzer IV has a clearly defined role, and it excels at it. The only problem is that nothing except the Tiger I has high enough DPM to fight against the IS-2, but that's no reason to change the JP4 entirely. JP4s do good enough against all other heavies.
Besides that, I do consider the Allied TD profile to be a bad design (even though we're stuck with it now), that I definitely wouldn't want to spread to even more units.
This narrative of yours that the JP4 is for countering mediums is ridiculous and no one is asking for it to be the case. The JP4 misses most of its shots at range trying to track mediums and Jacksons/Fireflies on the move, due to it having to rotate to keep up I imagine triggering the 50% moving accuracy modifier. What do you suppose happens to a turret-less tank when turreted tanks swarm it? The P4 is a much less risky counter. I'm not sure why you think a JP4 excels at countering other TDs either, it's nowhere close to a hard counter, it can only trade damage.
And no, it doesn't just struggle with an IS2, it also fails to do much of anything to an ISU even with HEAT rounds. Meanwhile allied TDs can reliable pen Elephant/JT frontally.