Probably not, since Marendar was created by Greg for the story.
While Lego had previously made a set of a story-only character by making Karzahni into a set in 2007, that’s not really possible here since Marendar wasn’t introduced until after the sets were discontinued.
Has anyone else noticed that the Jetrax T6 could be a prototype of the Thornatus V9, or vice versa (or that they came from the same prototype or something like that)?
The two vehicles have a very similar body shape (including a near-identical roll cage), and they both have transformative functions that change the vehicle between “parking mode” and “battle mode”. Additionally, they have similar armour styles, such as the inclusion of small blades alongside the driver, and the use of spiky parts in general. They even both use the Krika blade piece in the same location (if the Thornatus is in “narrow mode”).
There are other similarities as well, such as the inclusion of Midak Skyblasters on both vehicles, or the fact that their drivers have identical legs, identical colour schemes, and very similar arms, but those could just be due to the limited number of parts available to the designers.
The roll cage has been rolled between both vehicles in a roller coaster and a rental service. Why it happened is unknown, except that the two are apparently very similar.
Maybe the High Emperor will kindly explain it to us mere mortals why this is or is not, for it is by his will that such enigmas exist. All hail High Emperor @Ghid !