It's a catch-22. With chlorine, the ozone will deplete it so you'll have to add it every day or two and you'll use a lot of it even when you aren't using the tub. With bromine, the amount made by ozone will be a function of the level of your bromide bank. You could try and use a lower bromide bank and do not use tabs and just have the ozone produce the level of bromine you want. You would then just add more oxidizer after your soak.