Rolling X months on NPS Calculation

Currently, the pre-determined date ranges are a bit weird, especially early in the year as most of them are based on the fiscal year. It provides the current options: Current Month, Quarter, half year, year, etc, which are very limiting in the first part of the year.

Can an option be added to do rolling X months? Whatever the industry standard is? We do rolling 12 months, but I read that most should be doing rolling 3 months. 

I know we can use the Last X days option, but based on what I have seen, once that option is selected certain options become unavailable since it’s “customized”.