There is already a .NET prototype.
https://github.com/SteveSanderson/Blazor
https://www.youtube.com/watch?v=MiLAE6HMr10
WebAssembly without native GC support is no different that targeting a real hardware CPU. One just has to implement it as well.
As soon as WebAssembly reaches a more mature state, expect the resurgence of plugins and this time around we won't be able to disable them.