AVAudioEngine integration with Superpowered

Question

We have a project that currently uses AVAudioEngine as an audio solution for mixing audio from different player nodes. For the most part the solution works exactly to our expectation except for the AVAudioUnitTimePitch node. We're finding that the quality of time stretching is below our expectations and we have not been able to fix it. We're currently looking at Superpowered as an alternative, however I would like to avoid replacing our entire audio solution with the new SDK and would rather create a custom AVAudioNode that handles the time stretching algorithm, so that we can attach it to our current implementation and replace AVAudioUnitTimePitch. I'm a bit of a loss on how to achieve this and was wondering if anyone here had solved a similar issue and how they approached this? Thanks!