The Subframe is allowed as it doesn't modify the main suspension pick up point which is the inner TCA bracket, and you are allowed to run without a Anti Roll bar, the subframe mounts to its bolt position. The ARB can be added in the original position to the subframe anyway.
ARB would not be consider a suspension pick up point as on the cup cars they use lowering blocks therefore alterating its original position.
We ran like this in the VW Cup and the TRC South East Championship (class C) in 2004. And I was legal in it too with the black one i was building at the time, for class A. Obviously some specific champs may have specific regs that put the polo out, but most are alright afaik. Modification to Susp pick up points relates (usually) means relocating them. Rob Carvell got picked up on this on his scirocco racer in '04 if i remember. Also you need to keep the rear wheel well, otherwise you need to run in super production or whatever they call similar classes. Some organisers aren't too clued up on the polo and whats allowed, whats not - most think anything bar a cup car specific spec is out.
We did run without a ARB too originally with the subframe, but found it too stiff, sometimes say at Silverstone National Circuit, Boaksey was getting it on two wheels! Also ran 450lb front, 500-600lb rears
Can't obviously say about the 750MC but the BRSCC was cool with it.
