Maybe I'm missing something but what, exactly, is so iconic about the current bleachers? Is it the mystic lore of the pillars blocking your view, the creaky wood press box with exposed wiring, the lack of amenities?
Maybe it's the small stature of the place that makes it feel bigger than it really is. I really can't figure out why people are bitching.
As you mentioned, good architects can preserve all that with a modern, state of the art, structure.
I will have to admit that I almost fell off the toilet this morning laughing when Wejo suggested Austin being a possible replacement. Yeah, racing, or even watching, a 5k run at 2 pm in Austin would be so much fun in the summer.
What makes Eugene really work is their geographical location. It is a lot like Scandinavian track stadiums, weather that supports both distance runners and sprinters, small stadiums (less than 40,000 seats), motivated, local fans, with billboards hyping up the event/athletes. There is no where else in the US that could pull off what Eugene provides. So any improvements to those bleachers would be good for the sport.