I don't think it's that premature. Making the (big) assumption that serialization format X has good stable support in your language, and has the same expressive

I don't think it's that premature. Making the (big) assumption that serialization format X has good stable support in your language, and has the same expressive capabilities as JSON, you should be able to use it as a drop in replacement (as long as you control both ends of the communication...). And doesn't a huge portion of what we do around here amount to "shuffle serialized data around as efficiently as we can"?