I have found out that if I have two custom products trying to override the same Rendering Template (that's the case with the RadEditor and the BlueBridge Wiki Extensions for SharePoint which both override the RichTextField rendering template), SharePoint only really cares about the last loaded template (since they seem to be loaded alphabetically, RadEditorList.ascx takes precedence over bbWikiEditorV2.ascx).
Is there a way multiple rendering templates can concurrently work based on some configuration? (for instance, whether a site feature has been enabled or not?).