She's not insignificant, especially now that she's in the NOL.
Really, no character is insignificant in the plot anymore. They are all the 'chosen ones' after all.
And yes, Litchi is pretty deep. She has a detailed backstory, she puts on a cover of a normal doctor, but has so much to her. She also has the most options available to her in gameplay.
Though you can make the argument that no one in this game is *amazingly deep*, I wouldn't have much to say to that. I'm just saying Litchi is one of the deepest characters in this game.
Buuut I'll drop it, I don't wanna upset anyone over something this silly. :P