I'm glad you had a good experience with Protocol Buffers. (I work on the protobuf team at Google). But I would advise a bit of caution. Writing a fully-compliant protobuf implementation is trickier than it looks. I'd recommend running any new parser through the conformance tests; I created these to exercise some of the edge cases.

https://github.com/google/protobuf/tree/master/conformance

Here are some of the quirks of protobuf:

    - non-repeated fields can occur multiple times on
      the wire -- the last value "wins".
    - you have to be able to handle unknown fields, including
      unknown groups that can be nested arbitrarily.
    - repeated numbers have two different wire formats (packed
      and non-packed), you have be able to handle both.
    - when serializing, all signed integers need to be sign-
      extended to 64 bits, to support interop between different
      integer types.
    - you have to bounds-check delimited fields to make sure
      they don't violate the bounds of submessages you are
      already in.

I do think protobuf is a great technology overall. But it has some complexities too; I wouldn't want to oversell its simplicity and have people be unpleasantly surprised when they come across them later. :)