"any existing printer" changes every day, as does the driver set (the same printer can ship with different firmware levels, and these may require different/updated drivers). If you make such a commitment you are setting yourself up for a horrible series of failures.
I strongly suggest you avoid supporting such a claim if at all possible.
Assuming you still want to do this, installing CUPS will get you a bunch of basic printer drivers that ship with it. You should ensure that all the common printers you know about are on the list, and also gather up all the "less common" drivers and package them appropriately (you'll have to do this yourself I'm afraid).
This page talks about what you need to do, but for most commercial printers (HP & Canon) it basically boils down to "Make a package containing the appropriate PPD files, and make sure you keep them up to date", and for consumer grade printers it boils down to a lot of pain and suffering.