If Bay were to include them in the final battle in HK, it would make more sense about what Optimus Prime said: ''We need a new army''
I think that the human made caons are the stunticons... dead end is red with black! exactly the same colors that dead end has! that is a hell of a coincidence hum? in fact, all the man made cons are matching the stunticons colors! the optimus prime clone that galvatron has supossed to be may be motormaster and not nemesis prime would not be the fist time, the animated motormaster is optimus prime-like also and stinger/dead end is a recycled idea of dead end being a repain of another bot (jazz)