I'm doing some work to enable the purchase of auto-renewing memberships, using the UK-focussed GoCardless direct debit system. So far so good. One thing we've noticed is that the GoCardless API understands intervals in weeks, months, and years (with 1 year being the maximum). However CiviCRM's membership type duration unit doesn't offer 'week' as an option.
What would be involved in order to add 'week' as an option here?