Nice project! At Guardsquare, we have a similar project: https://github.com/Guardsquare/proguard-assembler

One of the things we use it for is testing: we can craft specific bytecode sequences that we want to test; for example, it's useful to test cases we've seen in the wild (e.g. obfuscated code) or to create a test that doesn't rely on a specific compiler/version.

An example of using the assembler from a ProGuard unit test https://github.com/Guardsquare/proguard/blob/master/base/src...