We needed this for our site. You can add as many 'domains' as you like, each with their own plan. Instead of creating a new customer + subscription we hacked together a way that each customer gets a unique 'plan', which can be multiple subscriptions. Multiple subscriptions per customer would have saved us a lot of time.

The other option was asking the user for CC details each time and creating a new customer at Stripe - but that felt like friction.