As I understand the issue is not only that the wanted bleed size could be different, but also that the bleed size is not correctly set in the incoming document.
If there is a method to identify from the job (either PDF information or other metadata) what is the wanted document size, then we can set the PDF trim box correctly. This can be done with Impose or Resize nodes.
After this you can set a dynamic imposition template to impose based on the trim box, and depending on the end size the imposition template should be able to accommodate the different formats.
I would like to know how to handle business cards with different bleed sizes in one workflow process.
E.g. Client provides cards in 2 sizes, 90x50mm or 85x55mm. However different clients send the artwork with bleed that ranges from 2.5mm up to 15mm (yes 15mm).
How can we setup (if possible) to handle a 90x50mm card without having to create different workflows with the different bleed sizes?