I'm not understanding why this is a Pilot Credit. Per USGBC's website.
"What is the Pilot Credit Library and its purpose?
a. The LEED Pilot Credit Library is intended to facilitate the introduction of new prerequisites and credits to LEED through stakeholder engagement and collaboration on the testing and analysis of proposed requirements. This process allows USGBC to refine credits through LEED project evaluations before they complete the balloting process for introduction into LEED... LEED pilot credits are, first and foremost, learning opportunities."

This prerequisite used to be part of LEED. What else are they going to learn about it by moving it to a Pilot Credit? There should already be a vast history of projects that have used this approach. Use that data base to find out the average kBTU/sf/year that was reduced using this option compared to the other options for this prerequisite.

Is there is a target for energy reduction? By saying LEED wants an Energy Star rating of 75 or better does that mean it wants a building to use 40 kBtu/sf/year less energy than an "average" building? Would it be acceptable instead to show the existing building reduced their energy consumption by 40 kBTU/sf/year? My concern with this is added complexity since each building type is going to want a different value for what's "average". Then everyone will be complaining about why their situation is unique and requires a different "average".

I prefer simplity and this 20% reduction was amazingly simple in terms of documentation. So I ask GBCI to look into their data base and calculate the weighted average energy savings per square foot for projects that had followed this compliance option. If the savings is close to the difference between an Energy Star 50 building and an Energy Star 75 building then I'd argue the simple 20% reduction option was a success and should be continued. If there's a large difference then maybe we consider a Pilot Credit with 'XX' kBtu/sf/year as the targeted energy reduction.