Tough nut to crack? Robot action?
Okay.
First of all, Gundam isn't about robots. It's not "Transformers." They don't have personalities and talk. They're mobile suits...they're fighter jets made anthropomorphic with arms and legs, piloted by people. Yes, they're mechs but they're hardware, they're combat vehicles.
"Mobile Suit Gundam," particularly the Universal Century material, is essentially the Japanese "Star Wars"...Amuro Rey is Luke Skywalker, Newtypes are Jedi, The Earth Federation and Zeon are the Rebel Alliance and the Empire, and instead of X-Wings and TIE Fighters, you have the Gundam taking on Zakus...then Doms...then Gelgoogs, etc.
It's the easiest nut to crack, especially if the intention is to adapt the original 0079/One Year War material. Treat it with the reverence, scale and drama of "Star Wars" and you're practically there.
As far as doing an original story, whether it be UC inspired or Wing inspired, I think it comes down to getting it across to audiences, again, that this isn't like watching Optimus Prime fight Megatron.
The drama is in the human characters and their conflict; the drama of politics and war, elevated into the mobile suit combat.
I think that's something that would not only be visually compelling but easily translatable so long as people aren't under some assumption that the Gundam itself is the main character.