If there is demand or initiative for a portable schema solution I'll gladly support it! The native architecture in the eno libraries is programmatic because that does have its own powerful merits which are employed to the fullest in the API design, like always there's not one best choice, and the 'validation creeping into code' can be turned around into 'external schema definition creeping out of line with code' just as well. ;) Do you have some concrete usecase in mind or planned where we could explore how a portable schema solution could look like for eno? Drafting things from various real life use cases has worked great for eno so far, so that's the route I would love to go here too if we follow that track!
Custom parser implementation is easier to answer: By now I've iterated through dozens of custom parser designs for eno in multiple languages, and I'm pretty much confident that generated parsers will not stand a chance of being faster, they after all do the same thing as I do, only I can't really hand-optimize what they produce afterwards. :) You can study the benchmarks I linked to under [3], there are some generated TOML parsers included with rather disappointing performance to put it mildly, and as it stands there's not much that's faster than the eno parsers in YAML/TOML land anyway, so I have low incentive to experiment in that domain currently. :) Long term goal is to (optionally) integrate (generated or custom) C (respectively Rust) parser cores through native bindings as well, so that will bring up this question again then for sure.