What was wrong with tank battles of COH? and how explosions worked? How infantry battles worked? What is the improvement to the new system?
The tank battles of CoH1 had the stupid 5% bug, random engine damage, the M10 misfire bug that Relic never fixed, and heavies only cost MP so fuel became a useles ressource late game. On the other hand, infantry snare was less useful and tanks came later. AT guns were just as effective, in CoH2 even Tigers and the like cannot loiter in their arc of fire without sustaining heavy damage (save maybe Jagdtiger and KT, but those units are stupidly designed), and a vet 3 PaK tears anything on tracks to shreds in seconds.
Explosions did work better back then. But that might be because we had nothing like the ISU-152. The big thing is inconsistency; sometimes my grenades will do a lot of damage, other times the same grenade, on the same target, in a similar position, barely dents them. Riflenades and US nades are especially prone to this.
Infantry battle is give or take. They were more lethal in CoH1, support weapons were fragile and we didn't have the ridiculous LMG dominance of today. On the other hand, no Truesight made ambushes impossible, there were several retarded abilities like Fire Up! (to say nothing of the OF bullshit) and snipers utterly dominated the meta thanks to how broken their cloak was.
Personally, the vCoH inspired changes I would (wishfully) see;
-delay all teching. Vehicles arrive way too early in CoH2, hell you can get superheavies at the 20 minute mark in a normal game, in 14-15 if you beeline in a team game. This is due to teching costs being similar to vCoH but in that game, normal points didn't hand out fuel and you didn't have fuel caches, and most maps didn't have high fuel points so even if you had a good chunk of the map you had, what, 20 fuel income? In CoH2 having a decent hold of the map + a handful of caches means a 30ish fuel income, that's much higher.
-Make all support teams more vulnerable. Maxims, MG42s, mortars, AT guns, this shit should die if it's got rifles pointed at it. A big part of the Maximspam problem is that even if grenadiers flank it, they take way too long to kill the crew with their rifles.
-Redesign stuff like the ISU-152. Long range. Good against infantry. Good against vehicles. Pick two. Having all three when you're not artillery is a no-no. And no fire through walls bullshit like the Jagdtiger, unless you're an immobile support weapon.
-Make all explosives, and especially grenades, more consistent. Have them have an ''always kill'' radius and a ''deals good damage'' radius or somesuch.
As for physics, I prefer the CoH2 ones. It was a bit silly seeing an armored car hit by a bazooka launch its parts all over the screen, and sometimes into deep spess. Tanks imploding from within looks better to me. And I like the death animation that leaves the vehicle's paint intact with a fire coming out of the top hatch.