I like this idea. As you said, it would help keeping the players interested and engaged between new content. Hosting a content like this also wouldn’t require too much effort on Fatshark’s part, making it a feasible thing to do.
This would be familiar territory for Fatshark, as there was a caption contest some months ago. There was a decent turnout. [ENDED] CAPTION CONTEST! Win a Rare 'The Eternal Serpent' Portrait Frame! (Vermintide 2)
Personally, I would love more chances to earn the Eternal Serpent portrait.