Yes, of course. But a few quick thoughts on that topic.
What is the difference between Savastano and Pettengill? Very simple. If there is no coherent, consistently-applied, office-wide policy, then the defense attorney does not need to offer evidence of disparate treatment between defendants. (That is, you don't have to show your client was treated worse than someone in a similar boat.) If there is a policy, then the defendant must show either that the prosecutor did not comport with that policy in charging your client or that your client was treated worse than the other guy despite falling under similar criteria.
What does "coherent" mean in this context? I tried to explain it here, in the context of the Clackamas County DA's office policy for aggregation, but I didn't do a good job. I think it's quite simple. (1) There is some criteria used to guide the prosecutor's charging decision. (2) The policy helps you identify what those criteria are. And (3), you know how the criteria impacts the charging decision. #3 might seem obvious, but if you look at the Clackamas County policy, it is quite hard to determine how particular criteria impact the decision to aggregate.
So take aggravating factors, aka sentence enhancement factors. They do seem somewhat arbitrarily alleged, at least in the counties I have worked in. "On supervision," while the most common aggravating factor, is only haphazardly alleged. There are plenty of reasons a prosecutor may not bother to allege the factor. The state may not be able to prove that merely being on supervision is a substantial and compelling reason to upward depart in your case. Or maybe it would be a compelling reason, but the prosecutor wouldn't expect any judge to exercise her discretion to enhance a PCS possession because of it, in light of the small amount of jail space that's available. But at least the essential facts of "on supervision" aren't in dispute. "Persistent involvement" gets a lot trickier. When it's worth it to allege persistent involvement is something that is more often than not only in the eye of that particular prosecutor and how worried he is that your client might otherwise want to go to trial.
All the more reason some policy is constitutionally essential, in order to make sure that defendants are treated fairly and consistently. That said, a coherent policy - inevitably designed by committee - will be hard to come up with, if it's to have the kind of specificity needed to ensure consistency. Hard but not impossible. The biggest obstacle to a coherent policy will be the disinclination of the DA's office to reduce their ability to charge enhancement facts whenever they want. And any coherent policy will, at least a little, reduce the DA's discretion. In fact, that's the whole point.
Once again, the steps that defense counsel need to take after your client has been given notice of the state's intent to seek an upward departure (or Dangerous Offender sentence): file an Equal Privileges challenge; subpoena someone from the DA's office to the hearing, asking them to bring the office policy on when to seek aggravating factors; depending on what, if anything, they bring, argue accordingly. If necessary, once you have the policy, ask for a setover to determine if you need any additional witnesses to prove disparate treatment.