Thank you Lee for submitting your feature request! I'll pass it to our team for investigation and consideration :)
At the moment, you could experiment with the Forecast report to see how much money you have available after all Scheduled transactions and future transactions are paid (Forecast report does not yet take into account your budgets).
If it helps to push this feature request to implementation sooner than later. One of YNAB's features to help manage and plan personal finances is to give every dollar a job. In practice it helps to know how much of your income has not been allocated to a budget and not leave funds up to spontaneous transactions.