The state of Ripley's voice these days makes her appearing as Gussie seem a grim prospect. But Henrik is right: Gussie SHOULD be played by someone easily distinguishable as older than the three principals (and Beth). Skinner has done and can still do it. I like the Ramirez idea, and she could probably read older (she's 36). Maybe even Julia Murney.
"You travel alone because other people are only there to remind you how much that hook hurts that we all bit down on. Wait for that one day we can bite free and get back out there in space where we belong, sail back over water, over skies, into space, the hook finally out of our mouths and we wander back out there in space spawning to other planets never to return hurrah to earth and we'll look back and can't even see these lives here anymore. Only the taste of blood to remind us we ever existed. The earth is small. We're gone. We're dead. We're safe."
-John Guare, Landscape of the Body