I can see possibly soldering some 10 or 12 ga wires into the 3.5mm sockets and then putting real bullet plugs on the end of the wires. Thats what I did on my Lehner motors that have 3.5mm sockets on the back of them also. Works great on the Lehners.
DOnt tell me its another esc than needs to moded to run well.
Can you measure the battery tray. How big is it on the inside dimensions? Just curious as to what size pack can fit into the tray.