They have done a live action Gundam movie. It's the god awful movie called G-Saviour. You wont find any new copies of the movie in the US as Bandai ceased production. In fact Gundam creator Yoshiyuki Tomino was vocally displeased with the movie.

As for the Robotech deal why not just do the suprior Macross which the first part of Robotech is based off of anyway.

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