Several actors who appear regularly in other series, or are main characters, but not THE main one, really need their own sitcom! Joanna Lumley first forayed into comedy as Jennifer Saunders's sidekick in "Ab Fab", but when given "Class Act", "Dr. Willoughby" and "Sensitive Skin" - she certainly proved her chops. Miranda Hart has, thankfully, been given her own sitcom and is showing the depth of her comic ability.
Who else needs a go?
I have suggestions...
In the UK...
Celia Imrie ("The New Statesman", "Ab Fab" - off the top of my head...)
Laura Aikman ("Teenage Kicks")
Ben Elton (So many - but never one of his own!)
Lucy Punch ("Doc Martin", "Let Them Eat Cake")
Alison Steadman ("Worst Week", "Let Them Eat Cake")
Adrian Scarborough ("Let Them Eat Cake")
Tim McInnerny ("Blackadder")
Ashley Benson ("Extras")
In the US
Madeline Zima ("The Nanny" - all grown up and has always shown comic talent.)
Portia De Rossi ("Arrested Development")
Jessica Walter ("Arrested Development")
Alia Shawkat ("Arrested Development")
Christine Baranski ("Cybill")
Kathy Najimi ("Veronica's Closet")
Mo Gaffney ("Roseanne", "Ab Fab" - there was talk about a spin-off with he
character - Bo.)
Becki Newton ("Ugly Betty")
French Stewart ("3rd Rock from the Sun")
Judith Light ("Ugly Betty")
<3