Further, like, protobuf now supports a Map<str, str>, although IDK about cap'n or flatbuffers. That lets you store the the common things in highly compressed p

Further, like, protobuf now supports a Map<str, str>, although IDK about cap'n or flatbuffers. That lets you store the the common things in highly compressed protobuf, and extensions can either be done via extension protos, or with stringly-typed map stuff for testing/weird stuff.