Can I get around the one (1) deferred prosecution limit on DUI's?

Probably not. The deferred prosecution statue RCW 10.05 restricts "Title 46" offenses (DUI's and Physical Control convictions) to one (1) Deferred Prosecution in your lifetime. One possible way around this may be to have the prosecutor agree to amend to a non-Title 46 offense (i.e. Reckless Endangerment {RCW 9A.36.050} or some similar offense) In today's political climate, I just do not think a prosecutor would agree to this - no matter how sympathetic the situation or the client. But it never hurts to ask I guess.