That's the thing though. A Panther can take on anything, and a Panzer IV can fall back to anti-infantry duty if it's got no mediums to club.
The Jagdpanzer IV is rarely the best pick. If you had the option to convert it to a lower RoF, higher pen gun, it'd be a safer pick.
I could say that building SU-85 in 2v2 preemptively assuming my enemy is going to build a PIV, PV, Brummbar or a Tiger is the same risk as for an OKW player to build a JPIV. If I build a T34/76 instead, I won't be able to deal with the armoured threat. The only SOV non-doc answer (that isn't a ZIS gun) to enemy armour is SU-85 and there are some horrible maps for 60 range casemate TDs like the ruins in Eindhoven (2v2). OKW does not need anyone feeling bad for them as they get all the tools in the game except for a sniper (though JLI come close). Having a good 60 range TD like a JP allows OKW to fend off enemy TDs and mediums. I think it fights TDs and mediums better than PIV and fights TDs better than Panther. Panther on the other hand fights heavy armour and infantry better than JP. Meanwhile PIV can fight mediums and bullies infantry. Each of these vehicles is better at something than the other one.
One second per shot.
That's an extra three seconds to kill a medium tank (as it doesn't reload the first shot).
In a game this fast, that's a big deal.
4.3 seconds to reload is about the same as the SU-85 or Jackson.
But with higher accuracy, higher penetration, lower cost (than Jackson), higher armour, higher health pool, etc. This change would affect teamgames significantly more than 1v1s. I think JPIV is in a good spot and should not be touched because balance is a fragile thing.