Putting a booster on a VS seems like a waste of money and energy to me. Why not just get a pressure cleaner that doesn't require a booster? ThePoolCleaner is a very good choice and requires less flow rate to operate.

But both a suction side and pressure side cleaner will require higher RPM from the VS to operate. So a robotic could save money if that is your objective. But there are downsides as well. Most manufactures recommend removing the cleaner immediately after the cycle is over which is a hassle. I am a bit lazy and like to leave the (suction side) cleaner in the pool and have it run every day.

However, one thing to consider is that a VS rarely has a lower lifetime cost than a two speed. Only in the most expensive $/kwh states (CA) does it make sense. The up front cost of the two speed is lower and it gets close to the VS in energy savings so it takes the VS much longer to pay for itself. In many cases, longer than the life of the pump.