There are hanging seraphs inside the hangar, and if you'll look closely you'll see that there are also Space Banshees docked behind force fields near there.
Is it possible to destroy the gun on the pelican? If it's destructable, that may lend more credence to it being a usable vehicle. And if so, that may mean that the seraphs will be destructable as well, if they can be entered. It's worth firing a rocket or two at those docked Seraphs to find out.
However, Pelicans are an interesting case, as far as vehicles go. There is no animation for entering them, whether it be the pilot seat or the gunner's. Even when using the switches on New Alexandria to fly one, you have to bring the nose of the craft near enough to a teammate for them to "get in", basically bringing the gun within the distance they need to "hold RB to enter". Piloting the pelican and manning the gun are two completely separate actions, required by two completely separate people. Seraphs are one-man craft, so I don't think it would work. Also, a pilotable Seraph is destructable, which goes back to what I said about trying to damage the ones in the hangar.
