All demographic non-sense aside, Rush would be fantastic for coachella. Their live sound is powerful, their catalogue is extensive, and their live setup/videos are nothing short of entertaining. And I'm on board with 2112 in it's entirety!
How long should they play? Intermission? Skip the drum solos?
Here was their 35-40 minute SARStock setlist from 2003. Not sure they've done another true multi-artists festival in 30+ years.
Closer to the Heart
Spirit of Radio
When I saw them in 2007, the show lasted about three hours including the drum solos and intermission. Any Rush fan would agree that it's far more worth it to catch a solo show, which is the case with a lot of older "classic rock" artists. But their obscure nature of festivals and progressive credibility would make Coachella a fine place to play regardless of set time.