I too have been searching for the perfect 10 minute virtuosic competition piece. There is Abegg variations by Schumann which is 8.45 minutes. Mephisto waltz is 10 minutes-but so overplayed. Ravel's La Valse I think is about 11 minutes. Liszt legend-st. francis walks on the water is 8 minutes. Mendelssohn variations seriouses is 11 minutes. Liszt hungarian rhapsodies are good, or perhaps the tarentella which is 9 minutes? He also wrote a 12 minute transcription of Totentanz, and Danse Macabre. Rigoletto parphrase is 7 minutes, but there is also the transcription of Norma which is amazing! I think that may be 15 minutes though. You could play Chopin Bolero or a Rondo-efective and underplayed. Dante sonata? Hope these suggestions helped.