Oh my, the Khachaturian Concerto...Bravo(I would call them like now, b/c that sucker takes some time to master)
I say, stick with your Clementi Sonata. It's not played enough and is quite a mature work. Instead of burning time learning another one, really nail this Sonata down because it deserves it. For your Romantic piece, I think the Ballade or the Spanish Rhapsody will fair. However, your suggestion of the set of Chopin nocturnes is very classy, of course be sure to choose the more difficult ones. Schumann, maybe try Papillions and Brahms, his entire or 3 mvts. of his Op. 119 (depending on time) or a set of his Ballades.
If you want to go outside the box alittle, Granados wrote some nice romantic pieces that's not played enough especially by the younger generation,.
Finally for your Etude, perhaps an Alkan etude to throw things off a little.