Maybe Bartok - Mikrokosmos and Kabalevsky pieces as student reference.
As bravurpieces you could select some transcription of Art Tatum perhaps.
So you're wondering what a balanced C20th program would be?Or what influences 'older' writing has had on C20th?There's clear Baroque influence in Bartok.Classical 'purity' I guess in Ravel, classical forms and wit in ProkofievRomantacism in early Scriabin, early Schoenberg, Rachmaninov, Strauss etc.Am I totally off the mark?