Separate options for prorating monthly or annual memberships

I want my monthly memberships to all prorate to the 1st of the month for cleaner bookkeeping.  I would also like for the annual membership to always be full annual memberships.  As a business, the goal of an annual membership is to lock in our members for a full year, by having to choose a "starting month" option, it will typically lock them in for less.  Currently, the prorated option is all or nothing, you have to prorate all membership frequency options, I would love it if each frequency had a separate proration option.