I have some experience with punishment enemas and with CBT/ballbusting but not the two together.

It would seem to Me that special care would need to be given when applying two risky/extreme activities at the same time. Overfilling or forced retention of an enema could lead to a rupture. Sepsis is a very real possibility.

Similarly, ballbusting can and does lead to ruptures which can be life threatening also.

The two are additionally in very close proximity... I am not saying don't do it, but I would recommend educating yourself on the risk, making sure the provider is also familiar with those risks, and having a mitigation plan in place for worst case scenarios.