BRAVE THEORY
Brave is short (Ness/Lucas Height). Quote stands at about that comparative to The Doctor, who I think is a regular human but I haven't played CS in forever.
Brave is relatively heavy (Mega Man weight-ish). Mega Man and Quote are both robots and roughly the same height, so they'd probably weigh very similarly.
Brave is slow(ish) on the ground. Quote's speed isn't too fantastic on the ground if memory serves, and it may be for balancing.
Brave is fast in the air. So is Quote, and he could be using the Booster 2.0.
Brave seems to play like a zoner (PAC-MAN, Duck Hunt Duo). Quote, with his tremendous arsenal, would also probably play like a zoner.
BRAVE rhymes with CAVE, and is one letter off BRACE (i.e Curly Brace). This one's a stretch, I know, but so are most of the codename guesses.