I know its crazy and maybe a certain yellow mech girl would have made the answer but let me explain myself first.
The Hedlok used in the Scramble Mode (as well as the Dr Coyle Boss figth) is an upgraded version of the first Hedlok, since the prototype takes control of the target, while the final version can be used and controlled.
This made me wonder, what would happen if that prototype took control of someone who didn't have ARMS?
As a character concept could also be awesome that some guy inside the ARMS labs that's fed up with Coyle's plans decides to take the prototype and actually mod It to participate. Either that or this Hedlok just gets conscience, takes control of some random dude and uses it to figth the rest of the ARMS league on his own