Why did EA end up cutting access to teammates earlier in the game & AR Vanguards

Recruitment missions are split up because the Xbox 360's disc size was too limited to fit the entire game. Some content had to be restricted to make room on disc one, and then more content unlocked once the story reached disc two.

Tali and Jack never had assault rifles. They always had pistols and shotguns. Sometimes characters carry guns they don't have equipped in cutscenes, which was for the animators' convenience.