Reposted from Surak-toc's "The abundance of ideas for a new trek show" thread. It's quite doable, even in senior cast members aged states. What familiar face would you like to show up in a series like that?
Several characters could be included as guest stars in a new series, as any officer serving in Starfleet could be capable of serving in an instructor's role; however, I think the value of a new Star Trek
series lies in the introduction of new characters or races. Cameo appearances by familiar characters are fun, but any series should feature strong regular characters, whether the plot includes the academy setting or another venue.