Ignition is very tightly coupled to the rest of V8, starting with that fact that it uses inline caches and the object model to maintain performance, and finishing with it itself being written in "CSA", which is an assembler DSL that is passed through the TurboFan (optimizing compiler) backend to generate the machine code for the bytecode handlers (this has the interesting side-effect that porting V8 to a new platform requires porting the optimizing compiler). There's not really much that can be split off.