Let's start from my opinion on current ammo situation. I do not believe that ammo is a problem we should be considering at least for now. Let me explain: if we forget that standard ammo even exists we are left with a pay to play game that has some questionable tanks and irredeemable dogshit maps that force you into close to facehug fights. If you accept the reality and choose to play the meta tanks you will quickly realize that armor is a real thing and that it actually works. My recent ranked experience shows that even with full gold you still have to aim carefully for weak spots (sometimes front of the turret is a weak spot cough 140 cough) and even then the pen isn't guaranteed.
What I'm saying is that meta tanks are so OP that if played well you need gold for even a chance of penning
As far as concept of flanking is concerned the previously mentioned maps make sure it remains a myth.
About the rebalance…
I consider myself above average
I'm perfectly fine with the proposed changes, even more than that, I fully support them. It is not going to change much and the changes are going to be very unpleasant most likely for people that are complaining about current ammo situation or at least for bad players. Special ammo is going to remain the primary type while the standard ammo is going to in my opinion fulfill the role of HE which is punishing mistakes. Good players are going to default to special ammo for snapshots and easier/guaranteed pen. Only if the pen is guaranteed they will switch to standard to punish the mistake made by their opponent regardless if it is over angling or picking a non-meta tank.
By now we have established that better players will have easier time punishing worse players (which is great) but here comes the kicker
Finally you poor souls driving super heavies will be able to survive for 2 shots longer but have you thought about actually OP tanks? Tanks that if played well are not only impenetrable for standard but very fucking resistant to "special" ammo? First of all they are getting straight up buff since increase in dmg is not affecting them. Secondly, in your mouse with current maps you are not flanking a chieftain to put this juicy standard ap shell in his side unless he is the dumbest motherfucker that managed to get a chieftain. On the other hand, at that point, as mentioned previously, a better player will be rewarded for outplaying his opponent with increase in alpha damage. So, now you are going to be even bigger HP pinatas for players with just enough brain power to tap the 2 key or die even faster if you make a mistake and get flanked.
To sum up, good / the best players with their meta tanks will perform even better while bad players will feel even worse because now they will get outplayed by standard ammo.
My suggestion is that instead of looking for excuses in the shiny ammo type you could whine about poor map design that doesn't allow for proper flanking, arty that makes at least me want to kms every time I try to push and a few bullshit tanks that deserve their own tier ( 279, 430U and chieftan).