Discover Scheduled Fixed/Rolling Report Date Options

The new calendaring options in Discover 3.0 are pretty amazing, but there is one outstanding request we have because the capability to do this exists in SiteCatalyst.  We would like for it to be possible to set a fixed start date on a Discover project date range, but have the end date be a rolling date.  Currently is seems only possible to do both dates as fixed or both dates as rolling.