M10 vs Panther - ha ha - yes we all laughed at that one - good joke - well done
Now can we have some vagley reasonable balance there?
M5 vs Puma - that’s fine, although I think a better equivalent for the Puma is the AEC Mk III with a 6 pdr gun - it has wheeled mobility like the Puma, and hte 6 Pdr is much more an equivalent to the 50mm L60 than the 37mm.
M8 vs PzIIIN - M8 looses a bit here due open top and no coax MG… but it’s not major… and below I suggest a replacement for this pair anyway
M4 vs PzIVJ - this is fine too as far as it goes, but there is a better duo that could go here and that is:
Pz-IVJ vs M10 - both of these are basically worse in Enlisted than the H and M4, so should arrive earlier, not later. Any advantage the M10 gets from the 76mm is outweighed by open top, no coax mg, and easily killed by all previous Axis tanks! Both have awful turret traverse speeds.
M4 vs Pz-IVH can then replace the Jumbo vs Pz-IVH - another good little joke - oh how we all laughed at this too… well done, you got us good…!!
Lastly the Panther and Jumbo - probably just make the Jumbo a 76mm and be done with it - neither can be properly balanced, and both should probably be premiums anyway at this stage - yes the Panther was a “normal” German tank of the era, but it was also completely outnumbered by allied armour so if you aren’t going to have any “real world” balance then make people pay for arguably the best tank of the campaign!
Other possibilties include Panther vs Firefly,or even the A30 Challenger - which was also available at Normandy, and has speed and a coax MG, if not well armoured.
Another duo that could probably be in there is Sherman 105mm CS tank and the StuH 42 - the “Stug” with 105mm howitzer - it is probably a better match than the M8 and PzIII IMO