I think the primarily-AOT compilation strategy we see today is a consequence of many of the initial workloads being frame-based animation where AOT avoids animation stutters. But this is likely to evolve over time as wasm workloads evolve. If and when we see wasm showing up in frameworks in contexts where page-load is the primary concern I can see a more lazy JIT strategy being the right thing and then we'd want to specify some sort of developer knob to control this. But given a pure-JIT approach like Chakra is using, wasm should be able to load code byte-for-byte faster than JS.