I agree that being able to separate your funds will be useful, and fund segregation into different pots is something that the team is already working on. There’s no ETA to share at the moment, but I’ll let you know once we have any further updates.
For the time being, we only offer single-use (disposable) cards that can be used to make purchases. While what you suggested isn’t in the works at the moment, I’ll forward it to the team so it is considered for future updates.
In the meantime, you might find it useful to customise your spending limits on a daily, monthly, and per-transaction basis. This is another way to manage your card’s access to your account balance.