From I quick look back at the pitch and review threads for SE-0215 (pitch, review) and SE-0319 (pitch, review) I was unable to find any extensive consideration of other protocols. Codable is mentioned offhand a couple times as another desirable target, and the previous Core Team guidance does not specifically request that subsequent proposals take a holistic approach and consider all possible protocols that might be useful:
I can't say with certainty whether I've missed a discussion somewhere, though.