Considering what they did with what they had, I'm not sure the 1939 Wehrmacht needed better tanks. What were they supposed to do with P4s? Beat France? That's what they did with P1s & P2s and a few P3s.
Perhaps they could have beaten France quicker but not by much, even if the whole German Army were motorised. They could perhaps mobilise and train more soldiers so they could take on France at the same time as they took Poland. But that would be a two-front war, which everyone thought was risky.
Besides the German motor industry was not up to the task of providing enough tanks, never mind sufficient lorries to motorise the whole army. The panzer divs which invaded France had a high proportion of Czech tanks in their OBs, thats how bad it was. They still did the business.
Just to reinforce the point, may I point out that during the year of Barbarossa, notwithstanding the dislocation, loss of resouces, movement of factories, etc, the Russians still managed to produce more tanks than the Germans.
BTW how come everyone slags off Goering? He may have been a lousy general and an unpleasant man, but he was a good organiser and had some highly capable subordinates. The superb German Air/infantry co-operation did not come about by accident.