A major overlooked reason why the centaur is better is that the centaur gets off a full burst in 2 seconds. For the ostwind to get off a volley (6 shots) it takes around 3-4 seconds. And the ostwind MUST be stationary for those seconds since we all know its accuracy is non-existant on the move while the centaur still has decent accuracy on the move. This is quite contradictory since people always say ostwind is more mobile than the centaur. But if the ostwind needs to stop for almost twice as long just to get off its shots, it's actually more vulnerable. And the ostwind is slightly faster than the centaur, but not faster than any allied mediums, so its mobility relative to its counters is actually a lie while it has paper armor while centaur bounces p4 shots a noticeable amount of times.
I suggest in addition to whatever combat buffs it gets, the ostwind gets a speed buff after vet1 to make it slightly faster than an allied medium.
What if they changed blitz to the old combat blitz where moving doesn't impact accuracy? I know normally it would be bad on an AI tank but we're talking about the istwind here and it isn't even that amazing when stationary...