Creator Killer: Free Radical Design. Haze was a new engine for a new IP on a console they'd never worked on before. A major gimmick was a task-based AI system that FRD paid for and then realized wouldn't work on the hardware they were developing for, meaning the game was making dead losses for them before they'd even started. Then came the elaborate pre-rendered trailers based on non-final scripts which had nothing to do with the final plot, licensed rap songs, and Rob Yescombe and David Doak claiming that making a game like Halo was "child's play." Since all their other projects were pitched on using the Haze engine, when Haze bombed all their custom dried up. Basically, Ion Storm all over again.
Development Hell: The game was delayed nearly a full year; the main feature, an advanced task-based AI system, had to be discarded during development, and early trailers bear little relation to the final plotline. Ubisoft demanded the entire plot be rewritten several times, with the setting changing from present-day to near-future and Iraq to a random South American country, even having the name of the PMC changed from "Mantle" to "Mantel." Seemingly worried that it would overrun further, Ubisoft then pulled the plug to prevent it clashing with the release of Far Cry 2; the result is an Obvious Beta with at least one level clearly originally designed for the other faction (the container ship was obviously supposed to be a Mantel level, given the player can smash steel bulkhead doors while the enemies have to use cutting gear), a cobbled-together plot and a general feeling of being unfinished. The engine was also a bad fit for the Playstation 3 and poor in general, the audio director likened inserting sounds into the game to "papering a wall while the rest of the house is burning down".
There's hints of the original setting everywhere; for example, the upper deck of the Land Carrier is made from the parts of a Nimitz-Class aircraft carrier — even including the catapult control pod, despite the final version having no CATOBAR aircraft. The lower areas are massively less detailed, indicating the original plan was for the finale to be the Rebels in boats trying to board an American carrier. Indeed, the Land Carrier even has small boats on board, probably the models intended for the original sequence.
The draft of the plot that most trailers (and the box art) were based on had a much stronger motive for people to join Mantel (it was a force for order in a violent, chaotic world) and had Shane come off Nectar extremely suddenly after a pair of Rebels ambush him and another trooper. They kill the other guy and slash the Jem'Hadar-like Nectar tube of the old suit design, followed by smashing the faceplate of his suit. The city map this was supposed to take place in was released as part of the second DLC map pack.
It's unclear how the co-op plotline was originally supposed to work, though there are hints that the idea was for each player to be one of the four major characters (Shane, Duvall, Peshy and Watchstrap). In the end, co-op mode simply has all four players see cutscenes as if they're Shane.