In all the affiliate plugins I've used - Goaffpro, Sumo Affiliates, Ultimate Affiliate Pro - we were able to set a separate affiliate name. For example, a WP user with the username "emil" could choose a different affiliate URL like "purewater", so their affiliate link would look like website.com/?ref=purewater. This feature is needed because users want to customize their affiliate links, and it's a common practice. I didn't expect not to find this feature in Affiliate Press.