I would suggest that bunq should not be more expensive than traditional banks. So 4 euro per month is fair. No setup costs, 1 free maestro card, 1 free debit Mastercard.
If the account number is a problem, include 5 accounts in the package and let users pay €0,50 per month for extra accounts
Extra maestro card; € 1 extra per month
Extra debit Mastercard: € 1 extra per month
Maestro transactions: unlimited free
Cash widrawal: 10 per month free, €1 per extra widrawal
Mastercard transaction: unlimited free