I think the main problem with 8/10 at 217 is the fact that 8 and 10 just get to be so congested sometimes. 8's a really a mess for much of its length.
The stretch from 8/10 on south probably needs the most work. I think if they're going to get rid of one interchange, Denney Road would be the obvious candidate. I'm not sure that the SB exit directly onto Scholls Ferry is all that necessary, either. The people needing to access Scholls Ferry from 217 SB could just exit at Hall Blvd (technically OR-141

) and take Cascade or Nimbus. The intersection at Cascade and Scholls Ferry could then be expanded some.
If they had a consistent 3 lanes per direction between 8/10 and 99W, that'd solve a lot of problems, I think, and eliminating the Denney Road interchange would probably make that a bit cheaper and easier.
The Woodburn interchange is probably one of the worst in Oregon and is screaming out for some relief or improvement.
No kidding. I've seen traffic routinely back up onto I-5 there from the SB exit ramp. They haven't done anything to that interchange (except install Flashing Yellow Arrows) since they put in outlet mall there.