Double-faced cards appear to have been handled differently by different maintainers at different times. The two main options are:
-Tell Lackey it's literally a card with a front and a nonstandard back, but then it can't be manifested or otherwise turned face-down except in a fully-hidden zone.
-Tell Lackey it's an ordinary card with the front and the usual Magic back, then give it a script to generate the backside as a token. You can't view the back in the deck editor, but it's more versatile in play.
The former is more convenient for deckbuilding, but the latter is better for play (in my opinion). I've coded the Rivals double-faced cards the latter way for now, but I'm open to suggestions.
I would like to go back and standardize this (and other inconsistencies) throughout the plugin.