Was any of those on a par with the Battle of Hannut for example?
2 French Armoured Divisions verses 2 German ones
Verses the British nothing that happened in TTL did not happen OTL (just more of it) - with the exception of a more successful Arras for the British
The Battle of Hanuut is a different in a few ways. Firstly it was fought to tie down French forces rather than as an actual attempt to break the French Lines. The purpose of tying down the French was to allow the Army group going through the Ardennes to Break the French lines. Yes it was costly but it worked. The difference to the fighting against the British is that there was no opportunity to create or exploit a weakness, no equivalent of the Army charging through the Ardennes.
The worrying question that the fighting against the British raises is what if the Ardennes attack had not worked. How would we be doing/ have done if we had been having to fight multiple Hanutt's to break the French and British lines. In that case a Breakthrough tank is a big asset as is improved tanks in general, better able to stand up to punishment in battle and keep going.
Sources are a bit lacking on this subject but from my understanding the OG Pz III turret actually couldn't take the L60. They had to make the rear walls straighter to increase available space and the gun was possibly modified. Now the decision to commit to the development of a L60 Pz III was not made immediately, so development could possibly still be brought forward a few months (someone mentionned 50 L60 Pz III or IVs being ordered but then cancelled after France, so this could pretty much be 76 Sherman syndrome where committing to making the gun fit wuld bring development forward earlier).
Pz IV couldn't take a 105 howitzer, that was what the OG VK 36.01 was for, but in the end they had no interest in such a vehicle. Skoda did actually build LT vz.35 prototypes with a new turret with their 47mm gun, but the Czech only requested one man in the turret while the Germans crammed two, so I doubt they could actually fit a bigger gun in a German Czech Panzer. The Pz 38(t) n.A could take the Puma 50mm turret but the German light tank lobby killed it anyway, and there's no reason to think they will suddenly be Notzis here.
I mentioned the 50-100 Panzer 4's given the L60 5cm gun. I'm sure the order was placed after the fighting against the Matilda's around Arras and Dunkirk post evacuation. Then after France fell the order was cancelled, I assume the reason they asked for Panzer 4's was because it could actually take the gun without modification.
I don't think it takes much for the Germans to press ahead with the Panzer 4 up-gunning so it may well have happened ITTL.
The interesting question becomes what happens to German tank production and procurement if the decision is made. If the support tank is getting the tank fighting gun does that mean the Panzer 3 gets the short 75 a lot earlier ITTL? or does the Panzer 3 get cancelled and the production switched to only Panzer 4's with either the long 5cm or short 75? The other option would be to try and fit the long 5cm into the Panzer 3 from the off rather than the shorter one but that still raises the question of what about the support tank?