If you're looking for something a little longer, try the Boulez 2nd sonata. Haha. Good *** joke.
don't use an etude to fulfill any requirement other than an etude requirement. The exception would be a set of etudes, like Stravinsky op. 7, Scriabin op. 65, or Bartok, op. 18, but these are all extraordinarily difficult sets. you can still add an etude to your program, and offer it at your auditions, but it should be in addition to rather than instead of a work that stands on its own.good modern pieces for auditions: Berg Sonata, any opus of Schoenberg, a Prokofiev Sonata, a Shostakovich p&f, Barber Sonata, Ballade, or Excursions, one of the 3-piece sets by Debussy, etc.
any of marc-andre hamelin's etudes would be a challenging and impressive choice.