Never played UT2004 - Ballistic mod? With some modding, you can do that in UT3 too, plus the fact that UT3 modding is MUCH better than GoW's... just compare the forums =). Also, GoW's cover system isn't that original... I mean, the "lean" move has been already invented before.
BTW, back on topic, it seems that DOW 2 will have VERY small squads, not only in the campaign... a tactical space marines squad is made up by 3 men... what do you think?