The glacier route sounds brilliant, though I am not exactly a svelt or accomplished cyclist. 4 passes in 4 days might leave me crying into my cup of tea but this is supposed to be an adventure so appeals greatly. I will leave that thought whirling around my noggin whilst I investigate all of the many other alternatives suggested.
The good news, part one, is that the grade rarely exceeds 6%. I think the absolute worst grade was 8% going east from Tonasket for 3/4 mile.
The best news is that half of the mountains is downhill. Whee!