Added a yellow coat to it.
Moved the oxygen generator down to the floor, since it was inaccesible from up there and you can't repair it during long trips.
Rotated periscopes, since the -90 degree ones, while looking cool put you into air, when used (if you were seated they put you so high, you'd drown due to your head being outside the sub)

It's a minibus sub. Front laser is only forward and activated by Navigation Terminal.