I think it’s a great idea! with Revolut you can have multiple cards.
I have one plastic and one metal and a few virtual attached to same account. All can be separately frozen, blocked, reissued, invidual limits set plus can disable contactless atm or online payments separately. Along with instant notifications and location based security. So I would say greater security and control can be implemented for single or double cards.
Saying that is a higher risk is translated as “we don’t think many will want it so will squash the idea before people like the idea”. So having one or two cards makes no difference to the security of any account.
It would be a good exclusive investor perk (especially for metal) to have these as additional settings. That way you can release a special plastic investor card (perhaps a recycled card or bamboo laminated for some crazy unique ideas) and keep peoples expensive to produce metal cards, plus offer exclusive features for them like the turning off of certain payment types for each.
I think this is a great opportunity to give give Curve distinct features.