I didn't think they'd be switching bodies either, but there's nothing stopping them making a combat platform like a reaper morph and deploying it like a more effective LOKI mech.
After all, the LOKI is bloody awful (and I seem to remember something in the ME2 codex saying they were used mainly for civilian security by companies too penny-pinching to shell out for proper security staff. The only reason they were in military use is that Sovereign and the geth killed a lot of soldiers during their assault on the Citadel).
As for the justification for a completely non-human-looking combat platform, well, the central disc has a better surface-area-to-volume-ratio than the human form and is therefore easier to armour. Four prehensile limbs are a better mode of locomotion than two, and can still deploy various graspers and useful tools from the tips. Finally, the weapons can be fired from cover with almost complete impunity, because the morph can crouch far closer to the ground than a human and just stick the guns over the top.
Plus, it just seems to fit with the Cybran methods of fighting - remote-controlled, highly-effective combat drone with an onboard AI for when it gets jammed, and the distinctive appearance is a lot more intimidating than a humanoid mech, especially once it's gained a reputation. For a
real nightmare, realise that the Cybrans use lots of cloaking, so
they're invisible as well. So are the infrared lasers they're firing. Good luck sleeping
!