For the single-movement Russian work, why not a late Scriabin sonata (5-10)?
Also, why not the Scriabin Fantasie in place of the preludes?
I'm looking for a light-hearted classical sonata, roughly 10-15 minutes in length, with more technical challenge. However much I love this sonata, it doesn't feel rigorous enough for senior rep.
I would be hard pressed to find a "technically challenging" classical sonata that is also light-hearted and 10 min long. You don't play classical sonatas (even Beethoven Sonatas) for their technical rigor, because there is more to being a pianist than being an athlete !! They don't show off your technique, they show off your maturity (this includes all 32 of Beethoven's Sonatas).