I'd wish for some Hannah Barbara shows dealing with more adult themes and issues. Maybe not Scooby or Jabberjaw, but a harder-hitting Josie and the Pussycats could be neat or even one of their superheros. Problem with that wish is, aside from Adult Swim not likely wanting to distance themselves from adult-comedic Space Ghost/Birdman/etc attempts, I don't know if lesser HB properties that's not Scooby-Doo would be that marketable nowadays.
That would be great... a throwback to early Adult Swim.
I would love a Hair Bear Bunch revival as a stoner comedy, or even a Flintstones show about Fred and Barney in college, dealing with off the wall situations.
But you're probably right, not much of a market for it now.