That would indeed be a good option.
I see two hurdles to overcome: wouldn’t the scenario you’re describing not be in alignment with card scheme rules? By now, it seems that still all cards have “only valid with signature” printed on the back. And if merchants aren’t sure if a card holder is the account owner, they are supposed to check the identity. While you can hand over a card to your partner on occasion, a merchant can deny to accept it, I believe. That might not be a problem in real life for the user at all, but it might be a problem if a card issuer want’s to offer a product that is designed specifically for this use case.
Secondly, I am not aware of any “challenger bank” with a mobile first approach and a streamlined account opening procedure with photo or video ID verification that has managed to set up this process for kids that aren’t of legal age. For opening a bank account, they need their parent’s consent. and it’s not just for services that are offered by Revolut, it’s also about services that are tied into Revolut’s product but offered by partners. All come with their own T&Cs that need to be aligned. And some of the additional offers that are embedded like travel health and device insurance can’t be offered that effortlessly to underage kids. Not to forget the fiat trading capabilities and crypto. I can see that all this adds so much complexity that all challenger banks decided to only offer their services to people of legal age by now.
When thinking about this, I can imagine a very limited version of an app that only allows to check transactions, to categorize and maybe to add a photo and block the card for security reasons. This app would run on a kids device, therefore location bases security would work. The kid’s account and card would be ordered from a parent’s fully fledged app, where parents handle the verification process, set a limit and transfer funds to their kid’s cards.
(Did you know that the founders of N26 wanted to set up a product exactly like this? A Mastercard Debit for kids, with an app where parents configure everything about their kid’s allowance. They eventually changed and became N26 instead.)