I’d appreciate if DuckDuckGo would implement this kind of speed badge to their search results. Never going to assume Google would even consider it as they sell the things that make sites slow in the first place.
Come up with a "privacy" or "non-tracking" badge.
Identify free-standing / independent / non-AMP sites.
Note simple and JS-free designs, or graceful degredation.
Well-formed page structures (microformats, HTML5), lack of obfuscated elements (JS, CSS), accessibility.
An open and distributed Web index standard.
Pretty much all of these are generally useful, and disadvantageous to Google.