Great idea and certainly one that I have thought of. This method is not without problems, since different protocols require different oxygen/ozone pressures. For example, if you ozonate a gallon of water as opposed to a glass of water, more pressure is required through the ozone generator to ozonate the gallon than the glass just because of the sheer molecular volume of the larger amount. I suppose your diverter could be equipped with a valve to compensate for this difference but it would have to be adjusted for each protocol. When you get in to stuff like rectal insufflation, the back pressure on the system is increasing as the insufflation time lengthens, so you would have to constantly adjust the diverter to keep the O2 flow to the ozonator constant. Even though these pressure gradients are very small they are sufficient to affect the O2 flow rates to both the ozonator and the diverter, making it difficult to keep a constant O2 flow to the ozonator. With changing O2 flow O3 - Ozone concentration also changes.
Flow meters of all sizes and configurations are available from companies like Cole Parmer or other lab supply places and certainly they could be added between the O2 supply and the ozonator for accuracy.
I suppose you could try to source out one-way low pressure valves and such to add to the tubing on the diverter and o2 supply to the ozonator. An oxygen regulator simply would not work here because it is designed to deal with 2200 psi.
Bear in mind though that most O2 concentrators only produce a maximum of 3 to 5 psi at any given flow rate. If the maximum pressure is reached and flow obstructed, the machine will usually shut off. Even my expensive little pediatric concentrator doesn't do a great job of insufflations because it is on the edge of not having enough pressure.
It would be great if you could come up with a system that worked.I wouldn't mind the loss of sales if it means that more people would experience the benefits of ozone. Its a higher cause than profit.