When I first came across the .NET Framework I was honestly amazed. Microsoft made a pseudo-assembly language that's entirely platform agnostic that works as a compiler target for numerous languages (C#, F#, more). And if you've been following the recent developments around WebAssembly this might all sound very familiar.
WebAssembly produced a great MVP but for WASM to really take off I would say that this issue is the most important. This issue describes interoperability with existing ES modules and giving WASM access to the Web APIs everyone knows and loves. With this, you could feasibly write a web app in any language*.
What do you think? Should WASM stick to doing math, or should the web get its own Framework Class Library?