@Axel: In the instance of Germany the situation regarding IBAN discrimination has gotten much better lately, though some companies still seem to employ some "softer" form of discrimination, by making you jump through additional hoops to accept foreign IBAN (over the phone or in writing, instated of accepting online form input). Still, I don't think there's that much benefit anymore.
Also, it's not like offering DE IBAN alone would enable you (quote) "to fully use bunq account like a German one" as bunq don't offer German girocards - though there's still places (smaller merchants) that will only accept girocard, often by way of creating plain SEPA direct debits from card data. Which would create additional implementation headaches.
Individual country IBANs are a pipe dream, not going happen in the foreseeable future. It's just not realistic. I'd be betting big money on that if I could.