There are more ways to make it transparent than exposing anti-spam secrets and here is few random ideas. First of all there is already CA system and there no reason why there couldn't be system where you pay for signing certificate to make sure your mail is always delivered as long as certificate reputation remain high. Imperfect, yet that would be much more reliable than current lottery system.

Another way to improve situation is to get rid of shady black lists BS like Spamhaus and replace them with proper organizations. Google could also create some consortium to improve protocols, implement easy to use mail servers that send everything properly out-of-box, then enforce DKIM usage, etc.

But no, Google need nothing of it because they have huge market share and directly benefit when non-Gmail services become unreliable.