Hot damn, there's even more arguing here than on the official forums. I've missed you guys
I think I saw the idea that CE isn't in PS2 because it doesn't mesh well with the class system, but someone in this thread on the official forums came up with a pretty simple and good solution to that. Also, I guess to add to the pages and pages of arguing, I'll say this.
CE requires skill to use effectively, just like shooting a gun, except it's a different kind of skill, which is already important in PS2. It can be effective if it's used properly, especially when used along with teammates (you might shoot at the people first, while ignoring the little turret that's unloading into your back. Furthermore, it makes base defense easier, which people seem to love to complain about. I'm not really gonna respond to anyone's argument, just sort of lay that out there.
Also, it's probably worth it to mention that, if you're interested, there was a pretty good idea made on how to utilize the ACE in PS2, which I copied and pasted into this thread on those forums.