Currently it’s impossible to purchase Robux or Premium with iDeal or anything similar.
The only options are Credit Card, Debit Card, Paypal or a Roblox Card.
However not everyone possesses any of those options.
In my case, I can’t get Premium right now without iDeal due to being under special administration. I’m allowed to have the subscriptions, I just cannot use any of the options available anymore because Paypal doesn’t allow people under special administration to make use of their services.
It’d improve my experience for sure, being able to use iDeal or something similar, and likely others’ too.