I have no clue if it's for a game or not - but I just think that risks are just a fun element when doing any form of storytelling, no matter the medium.
And yeah, the guy could be wearing armor - but there is no better armor than fear really. An exposed back would probably heighten vigilance as well as push one forward with much more fervor, seeing as how turning tail would most likely result in death - though I'm just conjecturing, of course. :]
Tactically, sure. But I still think this was made as a fun exoskeleton thing as opposed to a totally war-practical mech (the pilot's legs are sticking out too ya know XD).
Besides, though it's good to cover plot-holes and discrepencies for sure, you can't explain everything away when telling a story. Not only would the audience be bogged down with details, but they wouldn't have a chance to stretch the imagination. Personally, I'm loving coming up with ideas for why the unit may be like that. :3