As teachers, we know that we learn stuff best by teaching it to others. We also know that when a school becomes a demonstration site that teachers become ambassadors for the approach/frameworks that the school implements, reinforcing their ownership of that approach.
Finally, we know that when implementing a new approach, schools often bring in expert PD providers to work with them.
What if the goal of bringing in PD providers was to eventually develop the capacity of the staff to become PD providers/coaches themselves, both for other teachers in the school, and for other schools in the district/area.
When run well, the model would look like: Outside experts come in and provide initial PD. Teachers begin implementing, with outside experts returning to coach emerging teacher leaders in implementing with even more depth and skill. Outside experts then work in tandem with on-the-ground teachers to provide additional coaching and support within the school. When school becomes solid implementer of approach, it becomes a demonstration site, so subsequent PD (for other schools in district, say) can include a visit to the school to watch approach in action, and then PD from emerging teacher leaders who have been practicing the approach and know intimately the conditions in which the other teachers are working.
A model like this needs substantive commitment early on from the host school/district, but the ROI long term would be even more substantial.