I would love for my Credit card to be managed in the same eco-system as Monzo. Monzo has done wonders for my ability to stay on top of my finances (paired with YNAB) - and I think a credit offering in the same app would be nice.
I used to use an Amex for as many purchases as I possibly could (got to chase them rewards) but found I could have better control overall when everything was done in Monzo.
At the moment I only use my Amex on either high £ amount stuff, or retailers where I think “it’s better” to put it on the AMEX (just in case). I’d say really where I think I’d benefit from S75 protection - but I don’t have a huge amount of logic in that.