Directors Phil Lord and Chris Miller revealed in an interview with Yahoo! Movies that R2-D2 was intended to play a similar role as Batman in early drafts of the movie, making them one of the major players in the story.
“We figured we could get R2-D2 because his voice wasn’t a human being.” said Phil Lord, to which Chris Miller added, “A kid doesn’t have lawyers that won’t allow the toys to play together.”
The faithful droid sidekick to the Skywalker family unfortunately never appeared in the final cut, but there was a scene referencing the sci-fi franchise, which was inspired by watching a child play.
Following the purchase of Lucasfilm by Disney, it likely became increasingly more difficult behind-the-scenes to involve Star Wars in LEGO movie projects, considering they were produced by Warner Brothers, a direct competitor of the company. Since then, the production and distribution rights have moved over to Universal, another competitor to the house of mouse, so we probably won’t be seeing the droid trundle down the red LEGO carpet anytime soon.