Yeah, why not? If implemented correctly, this should ensure that the user interface is always snappy because all the slow parts (language servers, build systems

Yeah, why not? If implemented correctly, this should ensure that the user interface is always snappy because all the slow parts (language servers, build systems, search, embedded applications) would be in backends. Modern multi-core systems are especially well-suited to such an architecture. The biggest issue would be fragmentation of the extension ecosystem. The ecosystem would be split along implementation languages, which is an altogether disadvantegeous dimension.