Does the proposed intervention need to be well established in the clinic before the trial, or can it be implemented at the beginning of the contract and then tested against the more traditional intervention?

If the intervention is well established and you are taking it from one context and putting into another, it is reasonable to allot a period of time for that intervention to become established at that research site.

However, PCORI is not looking to fund new or untested interventions. Your Research Plan should provide clear evidence on why this intervention was deemed most appropriate for the study as a comparator.