I think the 10 foot idea wasn't bad myself since it really caters to everyone. Since the performers aren't real, why not make them huge and show off the awesome technology? No matter where you stand in the crowd you're going to get the exact same angle (maybe a little more flat than straight on), but not like the different angles you see with a real person. I think it was a good move, myself.
It also helps the fact that the Vocaloids only move back and forth across the stage, not up and down like real artists.
More I watch videos, the more I want to go. For real.