I believe James was designed to make sure there was at least one character that was thicker than the player.
This.
James' knowledge of the galaxy is comparable to Shepard ME1, with a sprinkling of ME2 knowledge.
Which itself is limited compared to a player who pays any attention to dialogue and codex.
He had his life on Earth (aka 'Pre-Service History') and an incident on Fehl Prime (aka 'Psychological Profile', limited 'Eden Prime', limited 'Collector Experience'). Then he chills on Omega (limited 'Terminus' experince).
In terms of 'knowledge requirements to be a useful ME3 character', he's right on the line, and arguably below the line. A relative newbie, and so the main companion for new ME3 players to be satisfied with. Liara for ME1+ players and EDI for ME2+ players.
EDIT: While I don't think MEA will follow so much of this format, I do think it is very possible to get at least one companion that has more of a connection to the trilogy (even if MEA ends up much more separated from previous games than ME2 and ME3 were), and at least one companion that can be considered the 'newbie to the franchise' companion. The rest/most of the rest being more general.