I had a $work-related project where a certain critical path could be optimized further by generating bytecode (the context was slightly different, it was for th

I had a $work-related project where a certain critical path could be optimized further by generating bytecode (the context was slightly different, it was for the JVM not cpython, and there was a DSL that had already existed before I joined the team which provided model structure and feature semantics, and the system was dealing with a lot of backlog at times so it was business-critical to improve performance on the critical path). You're spot on, the number one issue is that it becomes harder to debug (and there will be bugs no matter how many eyeballs are on the parser and IR and code generator) and harder to communicate. I'm sure the system was dismantled not long after I and a few others left the team. I did my best to document everything as I went, but I probably could have worked faster without that (and it surely would have been dismantled faster, too). The question comes down to how much you want that performance, and how much tooling you're willing to build around it. You can make some very custom debugging tools if you're already in there generating byte sequences around chunks of semantics. The mature languages have a lot of similar tools, too, though.