Thanks Tim for your feedback and request. We are looking at adding more flexibility in how you can bill your customers.
We are currently iterating and improving our active billing functionality. It would allow you to manage subscriptions for products or packages at a customer level. It would give you the ability to choose when you want to send the invoice based on the renewal date. This would allow you to send multiple invoices to a customer each month. Would this provide the solution you are looking for?
I have brought the feedback back to the team in regards to charge different customers in different currencies. Something we can consider as we improve our subscription management.