The problem is, they are not. Sure, they have the same joint system, but on the flip side, do you see people Plopping an exo force limb on a Bionicle because it has a balljoint? No. I mean, look at the brown figure, The entire upper piece, shoulders and head, is one piece. Even if yu could stick that on a Bionicle figure, the then the arms would need to be the same as the Ben 10 arms, making half the figure no different. In addition, the lack of pin holes or axle holes makes it so that these figures CAN'T be added on to.