If you have a broken accumulator, you would lose all the fluid very quickly, so having a second accumulator or suspension sphere assisted braking wouldn't make a lot of difference. The false sense of security that can be maintained with a merely flat accumulator would be lost in short order. In a late Xantia/XM with an anti-sink system, the suspension side would retain pressure and that may help for a short time, but every other model I've experienced drops as soon as you open the regulator bleed screw indicating that it has no pressure left in the circuit. It really means you have to look at the different piping circuits in different models to determine how it might behave. There would be a big difference in the outcome between having a flat accumulator and having a busted accumulator.