You're right about the market positioning - WebCC isn't trying to be Emscripten. It's for when you want to build for the web, not just on the web. I'm actually using it myself to port my game engine, currently in the process of ripping out Emscripten entirely.

On the opcode parsing - the switch/case approach is intentionally simple and surprisingly fast. Modern compilers turn dense switch statements into jump tables, so it's essentially O(1) dispatch.

Your flush timing concern is understandable, but the architecture actually handles this cleanly. Buffered commands accumulate, and anything that returns a value auto-flushes first to guarantee correct ordering. For game loops, the natural pattern is batch everything during your frame logic, single flush at the end. You don't lose control, the auto-flush on sync calls ensures execution order is always maintained.

DWARF debug support is a great call