As you can probably tell I am new to the scrubber concept but do have some would say an unhealthy interest in filtration in general!
From what I can gather the scrubber bypasses the normal nitrogen cycle so often referred to in every book on aquariums, ammonia, nitrite, nitrate etc. It does this by utilising the ammonia directly for growth.
If you had two independent screens and cleaned them alternately the filtration would be constant as long as each screen could support the tank alone. The poor bacteria would not be required and so all that expensive live rock would be unnecessary and more imaginative aquascapes could be designed.
Please tell me if I am missing something obvious.