It’s an interesting idea! I’m not sure 
can support this from a technical standpoint, but if they can this would be an excellent way to access different savings pots. Say that, for up to five savings pots, you could assign a unique PIN to each pot. Then when paying for something with the card, finds would be deducted from a savings pot based on the PIN you use when paying (obviously with a default PIN for the main account).
So if you’ve been saving for a weekend away, you then use that pot’s PIN when you are on your weekend break.