Ok so medium tanks are not supposed to kill heavy tanks in the open field? So what exactly are they for? To kill other medium tanks? Please, heavy tanks/ATGM do that better. Ok so maybe kill infantry? Nah cannon fodder tanks do that equally as well. Well maybe those medium tanks are good at flanking then and getting side armour hits on those heavy tanks?
Medium tanks can do the following:
1) Work better per-point than heavies against light stuff, including light tanks.
2) Operate near to LoS blocks without risking many points. The cheaper the unit the more dangerous the position you can put it in. The 350m extra range of heavy tanks means little if they can't see me until I'm 1500m away.
3) Allow your force to operate broadly, exposing the enemy side armour. Heavies in the middle, mediums on the flanks. Sure, as you say, you can reverse to keep range and prevent this, but in reversing you give me ground. In a lot of cases the only reason I'm pushing an area is to force you off the ground. If to be effective against me you have to give me ground then I'm meeting my objective, and the points lost in pushing you back may or may not make up for this.
4) Operate in an area which you cannot justify paying the price for a heavy tank. Maps are wide, and a single tank in the right place can do wonders. Sure, sometimes you'll want to go lighter, and sometimes heavier, but sometimes you want medium.
A lot of your arguments are valid if we're fighting in a staged battle a flat field with no cover and perfect information, however the game does not mirror this except in a few rare cases. Medium tanks will remain stronger than heavy tanks if you can find a way to close the range down without being fired upon. Obviously in an open field this is pretty tricky, but a very low proportion of most maps is open fields, and information isn't perfect.
1) Thats what autocannons and RR jeeps are for.
2) See 1.
3) If I lose all the map, but I have killed many more units than you then you having some more income is not going to change the fact that I can camp the rest of the game and still win. Or even just straight out attack you and beat you in a frontal battle since I obviously invest heavily in heavy tanks.
4) Maps that don't have open areas then sure heavy tanks are gonna suck, but so are medium tanks.
I'm pretty sure armies will now consist of 50% cheap stuff to keep LoS and keep enemy units engaged while the rest of the force will be heavy tanks with AA support. There really is no need for medium armour now, other stuff can do this well marginal role so much more effectively.