There is a point after you beat Saul on the Leviathan that you can go out in a space suit a second time (I think I was lost for a bit and did so by mistake). The problem is, since all the doors (incl the ones that you change into/outof space gear) would be opened at that point, there is no way to change out of those clunky space suits except for reloading the game
It definitely felt absurd walking around the Leviathan looking like the Michelin mascot not being able to use your weapons/items. I actually did encounter two sith grenadiers before I decided to reload -- quite a funny battle. You can still use force powers in that suit it seems, so I stunned the grenadiers with a stasis field and pummeled them with my big white fists till they died. Totally absurd!
Be warned, don't go out in a space suit a second time!
