Marigold could become an IT specialist on the station, or something, but I really can't see it happening. There's still lots that can be done with her storywise, especially in relation to Hannelore. In a way, barring some very major changes in Hannelore's future, Marigold is the closest Hannelore is likely to get to having a child. She even grounded her. Given her impulses for order and so on connected with her OCD I can't imagine Hannelore becoming a "pet parent," to use a stupid phrase, and using a pet as a surrogate for a child. She may like kittens, but I can't imagine her putting up with the physical mess they make for very long.
As for Faye and Angus I would imagine if they decide to make things more permanent Angus will initially move in with Marten and Faye. It's only fair given that Faye had to share an appartment with Dora when she and Marten were together. How long it will last is another matter,, as is what would happen to Marigold. A thought comes to mind that she would eventually end up with Dale as a roommate one way or another. No romance, just a good old fashioned "seemingly incompatible roommates stuck together" plot.