So far, I've been surprised at the lack of FOC Onslaught add-ons to make him more heavily resemble his appearance in the game - the only thing I've seen thus far is Treadshot A1's FOC Onslaught Upgrade Kit. With a little time and some spare LEGO, I decided to make my own add-on, seen below. The add-on pegs into Onslaught's hands in vehicle mode via two black TECHNIC pegs, and fits very tightly (but not to the detriment of the figure) in the rear gap. In fact, the tightness of the whole thing means that Onslaught's cannons no longer aim downwards. What purpose does it serve in robot mode? Well, I took a hint from Onslaught's Universe figure and gave him an awesome ballistic shield, which looks great when he's also armed with Brawl's gun. As it is, the add-on is very rough - in future, I hope to get some flatter/more sloped bricks that blend better with Onslaught's colour scheme. I guess this is just a very successful proof of concept! Some of these pics are pretty rubbish, please say if you want more (or a parts inventory).