I would like to see third-party credit cards include the card’s native currency at the time the card details are being entered. Top ups from each card would automatically be made in this currency, and Revolut would convert into the user’s base currency, thus ensuring the best rate.
+1 Also for debit cards. Just to restate this great suggestion in a slightly different way, there should be an option (configured per card) to restrict the currency of the top-up. It’s far too easy right now to accidentally top-up in say $ using a € card thus incurring fees from your top-up card issuer.