Sadly the re-routing feature got removed, but bunq is working on a new solution about this.
I came up with an (kind of old) idea about this:
Virtual Cards.
It is sooo simple, but just imagine having a virtual card for each bank account at bunq. Instead of manually re-route every merchant, you just use your virtual card for your online payments account at the merchant.
If the merchant changes the name he uses for payments, there is no problem - as he still uses the same virtual card for your "online payments" account.
And I don't know if I am alone here, but I personally would love to keep my online payments and offline payments separated, but currently I would need to "waste" one of my 3 physical cards for it.
This physical card would stay at home and would never be used for something offline.. for me this would just be "wasting" plastic.
In the US there is a company called Privacy.com (https://privacy.com/) - they are providing a virtual card for each website. Yes this would be kind of overkill, but providing a virtual card for each of your bank accounts would be a cool "Privacy.com" like experience - just for Europe.
I don't know what kind of solution bunq has about a new kind of re-routing feature. But I think with virtual cards you could do great thinks to solve many problems.
Especially with Apple Pay and (hopefully in the future) Google Pay (or at least Tap and Pay Mastercard) with much more merchants accepting it you don't need that much physical cards. Some banks are also already working on ATMs with NFC :)