I love ozone, and think it is better with chlorine and a waste with bromine. It reduces chlorine levels by burning off both cc and fc, but does not necessarily mean you use less to begin with. It just gets rid of the leftovers and byproducts.
Dichlor is almost half cya, and using it alone will cause high stabilizer levels quickly. You should switch to liquid chlorine (bleach) after cya reaches 30ppm.
I do not use mps. I add chlorine after each use and let the ozone take care of the cc, and the most of the residual fc. This gives me a "low chlorine" spa WHEN I USE IT, but does not mean I am using less chlorine.
In theory, ozone will oxidize bromide into bromine. But bromide and bromine are less reactive than chlorine, and from what I have gathered from those who use bromine, the ozone has no noticeable effect on bromine levels.
But it can take your fc from 5 to .5 overnight on a 24/7 injection system.
As for 4.6 turnovers... a 24/7 circulation system on a fractional hp pump (such as in your hot springs) is moving water at around 10gpm through the injection system. So if your spa is 400 gallons, that is a 40 minute turnover. 4.6 of those is 184 minutes, or about 3 hours for 99% ozone exposure. So 8 times per day your water is completely exposed to ozone.
Is there some theoretical risk? Sure. Do you still need chlorine? Yes.
Have I had any problems in the last 15 years or so I have done this? No.
Also, your jets running with the air injection on will aerate your water and raise your ph much more than the tiny bit in the ozone injection system. Close your air controls when not in use.
Just my 2 cents worth...