We are starting to create a little language in the toml key (time to re-evaluate).  We have constantly been tweaking the Decoders with new configuration knobs to handle more and more use cases (this will always be an issue).  The sandbox has proven infinitely more flexible and at the current time much more performant.  If the Go Payload decoders aren't adding any value (at this point they would have to be much faster, to justify their rigidity) is it really worth spending more dev cycles on them?