So it seemed pretty obvious to draw reference from the golems in dragon age for EDI and Legion’s look, though actual DA golems are pretty huge and bulky (and I think created from living dwarven volunteers). I’m not really sure of the exact nature of how they’re created but Mass Effect characters in DA is already enough of a stretch in regards to the lore. I’m thinking after acquiring Mordin and Tali in the Deep Roads Shepard would then come across a long lost community of golems and EDI would sort of be their leader/queen and Legion would act as her personal bodyguard. They’d be wary of Shepard at first due to their prior enslavement at the hands of their dwarven creators.
EDI: Like Tali she’d be an expert on darkspawn given her long years spent in the deep roads and her combat abilites would be similar to Shale’s in DA with an arsenal of different offensive crystal abilities. Also if you thought Joker had it rough before now he’s screwed
Legion: Fiercely loyal to EDI and somewhat overprotective, Legion wields a specially built in crossbow that he arms with crystals pried from his body.
characters left: Javik, James, Kasumi, Zaeed, and maybe Joker. Then I’m finally finished!