In watou’s solution you do not have to have a master/slave relationship with the controllers. A controller is set up for each location and I think watou centralized all of his rules to make maintenance of the rules easier. The controllers just share/duplicate their state and allow for them to interact with each other across a message bus.
Like I said, you don’t have to have one master controller. And even if you do, you can host a local sitemap on each instance and should the network between them go down you have a backup. But given your desire to keep your switches from being completely dependent on the controller it seems like this would be a non-issue. No controller, no problem, just use the local node relay directly.
I haven’t seen your other posts on this so I don’t yet know your reasoning or what risk you are trying to mitigate with your stand-alone nodes. But I will comment that many many devices follow this pattern. For example, all of my zwave devices can be controlled locally and it is only when I want to control them through OH (i.e. through the sitemap or through a rule) that the “controller” comes into the mix.
The limitation in OH’s phone apps is they can only connect to one OH instance at a time, and there is no way to limit what users can see and do based on log in. So by setting up a reverse proxy you are addressing both issues by applying separate authentication on a per URL basis and managing transfer of the web access from one URL to the appropriate URL on your OH instances. But this is itself introducing a single point of failure as the reverse proxy needs to be hosted at one location.
Again, it depends on your use case but you might try something like the following:
At your workshop set up the reverse proxy to do the authentication for your workmates and you. Also set it up so you can bring up your home sitemap when you are at the workshop. The reverse proxy’s URL should be configured for your local URL in the app. So when you are at the workshop you are accessing your OH instance there locally and not dependent on the network between your workshop and your house unless you want to get to your house’s HA, which the reverse proxy will forward it to.
At your house do the same only in reverse (i.e. the proxy forwards the traffic to the workshop instead of the house’s HA). Make sure the two URLs are the same on the two local networks.
Finally, pick one to be your main server for when you are not at either location and configure that URL as the Remote URL.
With this configuration when you are at a location you are only dependent on the network between locations when you try to remotely connect or when you are not at either location. The OH instances are also completely independent of each other. Finally, because you are using the same local URL you are able to access both locations from the same app without needing a Master Controller.
About two minutes of Google shows that you are likely to have the same problems with NodeRed.