I cheerfully envy you both, although my study here has been priceless, and is ongoing.
It would be most rewarding to sit down and practise 'sample performance' skills, refining and honing, using the orchestra between the ears to draw nuance and texture into the medium. My picks for this exercise for the future would be Saint-Saens Organ symphony, Beethoven's 8th, and Shostakovich 7 and 11, and then graduate to solo instruments, e.g. Bruch's Violin Concerto, Sheherazade, etc.
JWL, your premise of practising with known works to enhance performance with self written work rings with me too, and i think this method of skill emhancement would definitely raise the bar, and keep the standard up. It would also prove a worthy critique of orchestration versus sample performance limitations. No hiding!
Strauss's Elektra and the outstanding orchestration would be my choice in his work, along with another great test for string performing and interpretation, Sibelius' Swan of Tuonela. I've listened to this regularly once again, and there's a lot to consider.
I also think the Grieg Piano Concerto would be enlightening. (Something i was performing before my accident. A most enjoyable piece to play and intepret, IMHO) Wagner too, with the Prelude to Lohengrin, and Tristan, promises much as a challenge to improve skills.
One thing is for sure, orchestral experience counts for both good and challenging.
We know what we hear, and expect that in the end result. The method of obtaining that will be a reflection of how skillful we are in sample performance.
As a brief aside, the worst piece i ever had the misfortune to conduct was The Gondoliers. Page after page of offbeats and little else. I went home after each night's performance (6 week season) and railed in frustrated boredom to the sounds of Beethoven, Mahler, Wagner and Shostakovich, just to maintain a foothold in sanity!
Regards,
Alex.