The bandwidth on FTTC allows for a lot of units to be used very quickly at peak times, so it should be possible to configure a different line rate for peak/off peak/night.
There would be the option to use the actual line rate for each period (which would be the default).
The actual line rate (if lower) would override the set value.
Special usage periods (e.g. Christmas) would be handled as the nearest type (i.e. night).