I don't think there are a lot of tank destroyers that meet your archetype.
wrongway
I don't know anything about tanks historically. What I'm thinking of is whatever vehicles that'd add variety to the current ground battle. Looking thru Tarrif.net database..
Panzerkampfwagen V Ausf. G "Panther" - 28.75 mph. we got this one
Panzerkampfwagen V Ausf. D (A1) "Panther" - 34 mph,
75mm KwK 42 L/70. unless I'm mistaken that's same gun as Panther G's. Armor is the same except 10mm more than G model's 100mm turret front. So faster and a little more armor than the G we got. Why did we get the G?
Panzerkampfwagen V Ausf. A (A2) "Panther"- same speed as our Panther G - redundant
Panzerkampfwagen VI Ausf. B "Tiger II" - 24 mph, too slow
Jagdpanzer 38(t) "Hetzer" - 26 mph, too slow
Jagdpanzer IV / 48 - 25 mph, too slow
Jagdpanzer IV / 70 (A) - 24 mph, too slow
Jagdpanzer IV / 70 (V) - even slower
StuG III Ausf. F - 25 mph
StuG III Ausf. G - same
StuG IV - even slower
Jagdpanther - 34 mph
88mm Kw.K.43 L/71 with 10x, 7° sight. Same armor as the Panther G.
is that gun any good? Doesn't look like the same 88 as our Tiger. It looks like it's got better ballistics and significantly more penetration.
Jagdtiger - too slow
Marder II Ausf. D/E 34 - little armor and not that fast to offset it.
Sd.Kfz.234/2 (8 Rad) "Puma" - 50mph: Slower than M8 and gun looks similar - redundant.
Sd.Kfz.234/4 (8 Rad) - 50 mph,
75mm PaK 40 L/48: Same speed, better gun, worthwhile? It ain't pretty.
M18 Hellcat - 50mph,
76mm M1A2 L/55 with 5x, 13°
Armor Piercing Composite Rigid seems like only round competitive with Jagdpanther gun. Barely any armor but very good speed advantage.
M36 - 26mph, too slow
So it's either M18 or Jagdpanther. The Jagdpanther's very slow but the optics and gun look like in a class of their own. The Pz.V Ausf. D (A1) Panther looks good but too redundant with the G we just got.