One query - The current research assumes that all countries acheive a good quality design at the end of the reseearch.
However, the British anti-tank gun (the 2 pounder) was dreadful, woefully inadequate with poor pentration - the shells would simple bounce off the Panzer frontal armour.
Relative to what?
The German equivalent to the 2pdr, the PaK36, penetrates 63mm of RHA with its Pzgr.40 round (APCR) @ 100 meters, 30 degrees from the horizontal. It'll penetrate 22mm @ 1,000 meters and at the same angle. This is more expensive tungsten round and you can expect its regular solid shot Pzgr doesn't even penetrate that much at close range.
The 2pdr penetrates 73mm of RHA with its APCBC round @ 91m, 30 degrees from the horizontal, and 57mm @ 914m. In other words, the 2pdr has more penetrating power than the German light anti-tank gun using its expensive Tungsten shell, and being solid-shot with a ballistics cap it also holds penetration far better at longer ranges and more oblique angles.
The 2pdr can penetrate the front hull and turret of a Pz.IV without the reinforced hull armor to at least 1,000 meters (50mm FHA both), only failing to penetrate the hull when the 30mm Applique FHA plate was added to the hull putting total protection up to 80mm. The story is similar with the Pz.III, where the 2pdr can handily knock out the Pz.III's 50mm frontal and turret armor to about 1,000 meters, only struggling heavily once the J1 variant and up introduced additional 20mm RHA plates on the hull and turret. The sides and rear of the Pz.III and Pz.IV would essentially be free game for the 2pdr at any range it could realistically be expected to engage at, regardless of model.
The German tanks that would be able to bounce or shatter the 2pdr with ease are the Tiger, Panther, and many of the heavier german Assault Guns and tank destroyers (StuG III G, Hetzer, Jagdpanther, etc.). That's not really an insult to the 2pdr though, since this design would be at least a half-decade old by the time these arrived en masse and no light anti-tank gun would be sufficient at destroying these. (Even the 6pdr would struggle to some extent, a 17pdr would be preferable to consistently penetrate most of these vehicles.)
If a player is still producing 2pdrs when the German player starts to produce Tigers, the British player is going to be unpleasantly suprised anyways. The 2pdr was perfectly capable of dealing with common early-war armor and was still capable of penetrating many tanks commonly encountered on the Western Front, and since the gun was physically fine itself I don't see any value in a mechanic that nerfs the gun based on what is basically hearsay
(At these small levels of penetration, the stricter German criteria for their penetration would only add perhaps a couple of millimeters if adjusted to be equivalent to British criterion, so I've neglected it.)