We're heading to New Vegas in Season 2, and this is the only character I really would like to see resurface, mostly because Yes Man saved me from never finishing New Vegas. I was starting to get bored with the plot and Yes Man brought me back in.
Dave Foley killed as it Yes Man, and I would love to see him back in the role. I was a big fan of Foley from Kids in the Hall/News Radio days, and I was overjoyed when I ran into Yes Man and recognized his voice. Dave Foley has exactly the kind of absurd cheery demeanor a character like Yes Man needs.
Further, I'm going to assume the Courier/Yes Man taking over the Strip ending of New Vegas probably isn't canon, it means there's ample opportunity potentially for Yes Man to continue being the best Yes Man that he is.
Hell, I'd love to see any of the Kids in the Hall in Season 2, honestly. Kevin McDonald keeps looking weirder every fucking year, he would fit in with wastelanders. Hell, the new Kids in the Hall season was an Amazon Prime show, and both Kevin and Dave went full frontal nudity with their weird old bodies. They're the right kind of fit for the wasteland.
I would also think Foley's "Doomsday DJ" sketch is a great example of why they need him in Season 2 of Fallout.
I second the idea of getting other KitH cast members involved. Have Scott Thompson voice Marilyn or Light Switch #3.
Mutant Buddy Cole.