I don't think this would solve it. Elephants are rarely seen in 1vs1 because they cost more than a Tiger and have a very specialised role. They can do one thing very good, so they best thing to counter them is stop building tanks, and build more infantry, to which the elephant can do nothing.
The reason Pak43 works sometimes in 1vs1,(and would more often if stupid one click delete abilities get a nerf) is, it costs no fuel. You mostly build a pak 43 if your opponent has more tanks than you, because he had more map control and so on. In this case, you have no fuel and just manpower so its a good Idea to build the pak, because you cant counter his tanks with your own tanks.
If we now made the Elephant in a mobile Pak43 which costs a ton of fuel, why would you ever want to build it in a 1vs1? It has the same role as before, it just has become better in it. In a 1vs1 scenario you will never go for an elephant if you can go for a Tiger, which is cheaper, does amazing infantry damage as well as good anti-tank. So to solve this problem, you have to give the Elephant more utility so it has a use outside of pure AT. Ideally, it should be your go to tank if your facing allied tank destroyers or heavys.
I think a barrage would be the best thing, even if its just copy paste. Maybe add with vet a second type of barrage similar to the pack Howie, there it fires AT rounds which do heavy damage to vehicles only. This way the elephant would keep some sort of long range At, but this time it's avoidable by the opponent.