After posting a short proposal in the KeePass forum, I thought it would be best to set up a SourceForge project right now, so that the thing (a) gets a name and (b) has a place where notes, documentation, and discussions can be kept together.
It turned out that the obvious name for the plugin, "KeeCard", was already taken - by a project created by Chris Peterson. That project really didn't get far and seems dead for a year now, but is still labelled to be in Planning stage. Hope this is not a bad omen ...