Maybe a panel of maintainers could publish a quarterly review with attribution/thanks to the most important contributors. No metrics to game, only pure human expert opinions.
[Generic hand-waving about how LWN kinda does this, in a high-signal manner unfriendly to statistical summation]
IMO part of the problem is that Greg KH publishes this annual 'state of the kernel' that is just a list of metrics to game. Which feels like it was started to shame non-RH companies to contribute more often. So, kinda maybe beware what you wish for?
Maintainers aren’t interested in taking on extra chores. However, important contributors already do receive attribution, in the format of news articles, here: