The problem with "lack of classes" is that every non-trivial program makes its own implementation of something-like-classes, but built on top of metatables.
So before you can start hacking on anything in Lua, you have to first understand the class system, which may or may not be documented.
I did similar synth reverse-engineering of DS-10 synth from Korg for Nintendo DS, so not much desoldering involved :-) The goal was to get it running as a VST plugin, but ARM emulation wasn't fast enough, so I wrote a static-JIT decompiler and decompiled the synth portion of the code into C instructions (see "c-code.h").