It definitely needs more variety. An hour of "Home Movies" is too much, and frankly so too is an hour of Williams Street productions (and I say that as a die-hard fan of SG:C2C).
One problem, I suspect, is that to excuse them running shows like "Cowboy Bebop" they feel they have to construct a lineup that is entirely offputting to younger viewers, so they go for jittery, illustrated radio fare like "HM" and "ATHF" and "Brak Show" and the rest. It's too much.
I'm thinking they need to loosen up and think of the Adult Swim block as an alternative-style prime time block. They basically have the elements in place: Sitcoms, hard-edge dramas and a late night show. Maybe if they put it together as a parallel night-time schedule, something like:
10:00 The PJs (or some such sitcom type show)
10:30 Home Movies
11:30 Williams Street Theater (rotating SeaLab, Harvey Birdman, Brak & ATHF)
11:45 Cowboy Bebop
12:15 Cowboy Bebop (or Trigun or some other anime)
12:45 Space Ghost: Coast to Coast
That way you could start off with something relatively tame and safe for kids, and would gradually edge toward more "adult" stuff as the evening progresses.