What should a pilot be required to demonstrate?

Whatever the conversion decision will actually be argued on, written down before the pilot starts.

In practice that usually means a measurable primary outcome with a baseline captured beforehand, a defined population and setting, a stated duration, a named owner, and an explicit statement of what result would lead the organization to decline.

The last element is the one most often skipped and the most valuable. A pilot that cannot fail cannot demonstrate anything, and committees know it.