: But there weren't any Pfhor stationed in the Citadel... So
: were staircases thrown in for the sake of convenience, or is it because of
: some ancient Jjaro conspiracy? ;)
This is something that always bothered me, too. And why do the doors just happen to be of human proportions? If we want to keep this consistent with story, I would say that the Citadel was originally built for the Jjaro, who probably couldn't fly.
The only realistic S'hpt-only ship I've seen in a Marathon Scenario appears in the Scenario Marathon Dissent, which takes place outside the Marathon Universe (the S'pht are called something else). There is a level in Dissent that takes place in a S'pht ship which lacks elevators or stairs. The player must start at the top and eliminate all the S'pht on a layer before jumping down to the next one - failing to do so necessitates starting over.