More Start-up would be boring. I never really got any good ideas that would make sequels not feel like the same thing over again.
Miss Thursday though... I think I got too silly with one pitch (Sissy and a very-Velma friend try to solve the mystery of what made her brother such a stud) and too legally-actionable with the other (Dark Phoenix, anyone?).
I liked the X-Men spin off one, I think I still have that script somewhere. Might be doable with some adjustments.
Never saw the Velma-ish one though...
Had fun with Miss Thursday so I wouldn't be opposed to doing more.