So I thought the SEV and LER are based on the same design principles (share the same chassis etc.), the key design element being an enclosed enviroment, the cabin would (under normal circumstances) never be depressurized, you enter/exit through the airlock directly from the Hab, and EVA out the back (eg. LER). The design advantages being; max comfort, max space, and very important, keeps the dirty dusty EVA suits outside!
The back of the SEV is split in two and has two kinda windows? so I initially thought these doors open up and you have the suits like on the LER, but the doors then have no purpoe, so why? Now if the side hatches? open up you have full depressurization, and that opens up a whole new can of worms! Maybe makes more sense on the space version? but why not just use the airlocks for EVA? Or maybe the SEV is not intended for EVA at all! And as you mentioned the round airlocks and the rectangle Hab airlocks conundrum.
The more I look at it the more I think this is a concecptual mockup, artist impression, and not a practical design.
So my suggestion for in game would be: forget about the doors entirely! simply EVA from the airlock, an action area at the back for tools/cargo, nice 3d cockpict (lots of pics of that), + crab walk & dust effects and we got one sexy space truck