Personally, I think it is entirely feasible to learn a Ballade with only a waltz under your belt. Personally, I learned Chopin's ballade no 1 having only learned the Waltz No. 1,3,7; Nocturne in C# posthumous, and three opuses of mazurkas. This being said, I do not understand why one can not tackle a Ballade after having learned only a waltz.
@OP: In response to your question for a good all-Chopin program (60-min recital, perhaps) I'd suggest the following.
Ballade No. 2 (this is considered by some to be the second hardest ballade, after Ballade no 4. Obviously Ballade no 3 is easiest, but it seems that there is considerable debate regarding if Ballade No 1 or Ballade No 2 is harder.) This seems to be the perfect Ballade for you - in my opinion it is infinitesimally easier than Ballade No 1, but Ballade No 2 presents extremely different technical and musical challenges than Ballade No 1. This was my second ballade after Ballade No. 1.
Scherzo No 1 I've just started working on this one. It is certainly harder than the Scherzo
No 2 (and perhaps No 3, but I am unsure) and is very similar in difficulty level to the Ballade No 1. If you haven't played a scherzo this one is perfect.
Barcarolle This is a true gem, but despite how easy it sounds, it's surpirsingly hard to play. The effort is worthwhile however, as this is one of Chopin's most gorgeous pieces.
Polonaise-Fantasie (or polonaise in f# minor)
This program so far would take roughly 40 minutes. For the remaining twenty minutes, I'd say doing a few waltzes, or a few opuses of mazurkas, would both be great. Nocturnes wouldn't be bad either. At this level, you should probably stay away from the sonatas ....