Alcatraz is just a Gordon Freeman knockoff. I want Psycho! He's funny, awesome, and he's British you muppet!
Though it would be cool if all the characters returned for a final showdown against the Ceph. Nomad with his TAC launcher, Psycho with his PAX gun, Alcatraz/Prophect with his MOAC, and Helena with her anti-alien signal!
There is an interesting theory to what happened to the main characters of the first game

Psycho, Nomad, and Helena were killed by an infection alrite. It was an infection of entitled COD loving console fanboys who didn't want to be left out plot-wise because they were too lazy/ignorant to get good PC and Crysis 1. Nomad fought back by saying "we have to resolve plot holes." But the fanboys just continued there zombified ranting "Me no want lean" "What is DX11? me scared of it" "No prone, more like Halo" "Me want gamepad and 540p rendered graphics!" "Gamebreaking killstreaks, MOAR GAMEBREAKING KILLSTREAKS!!!!!" "BRAINS!!! We have no...BRAINS!!!". They slowly infected them and they decided, their minds destroyed by the infection, that they must abrubtly dissappear from the Crysis storyline to appease 12 year olds and college frat boys who play consoles.