As long as it doesn't affect crowding too much I would consider reducing the frequency on those turn up and go routes.
The problem is with that approach is: what do you do with the buses that you make redundant by reducing the frequency ? I hear people saying that you still need them for the busy periods. Then the finance dept start saying why do we have a thousand (or two) buses that are only in use 4 hours a day ? - we can save £X million a year if we get rid of these under-used vehicles and not have to pay drivers, etc to operate/maintain/clean them.
An idea - buy short buses that you can join together into longer buses for busy periods................hang on though, I think that other transport suppliers have already tried that and you just end up with short buses most of the time............