MicroLua currently compiles Lua files to binary at built time. It seems that Fennel is capable of transpiling to Lua source code, so it should be easy to add that step to the build process.
I have to admit that this was one reason why it took me so long to start a project with Lua. Now that I've had some exposure to the language, I can say that it's not as bad as it seems, but it's also not "nothing". I frequently have to think about indices to avoid making mistakes in Lua, while in zero-based language indexing is pretty much muscle memory.
I haven't run any benchmarks yet, and TBH performance isn't a high priority, but event dispatch latency is currently fairly bad, between 100 and 150 us (when overclocking the Pico at 250 MHz). It feels like it should be possible to bring it down to <30 us. I suspect the bad latency is due to my very naive implementation of thread scheduling and timers.
I can't really give advice for creating a new language, or even for creating a new implementation of an existing one. MicroLua uses the existing Lua implementation from lua.org, and just packages it to make it useful on a specific platform.
For that, it helps if the existing implementation is already cross-platform and has few dependencies. Lua is great in this respect, as it only depends on a libc. The first step is to get it to compile for the target platform and have it execute a hard-coded "hello world" script. After that, it's only a matter of adding more libraries, one at a time.
