[zerovox]

Unless I'm missing some of the problems you're trying to solve, this seems like an extremely over engineered solution to the problem of code duplication (like validation) and boiler-plate communication code. For the former, if you're using a node backend, you can pretty trivially reuse the same code between client and server side. The later doesn't really seem like a big enough issue on its own to really warrant an architecture that requires a back-end with per-tab mirroring - you can usually encapsulate the 'cumbersome AJAX calls' with a straight forward API (or GraphQL query if that floats your boat).

This approach also forgoes many of the nice side-effects of having a clear slide-server boundary like avoiding leaking implementation details into your front-end code. Also, a simple REST API can be reused across platforms, so when you want a native experience on Android, iOS, etc you wont have to replicate this architecture or the underlying logic on each of those platforms.