Gizmo, Web Gizmo, MC Client, and all DLNA controllers all have exactly the same problem. So they don't work properly with multiple zones. Although that is unfair. The remotes are fine, it's the server they're connected to that doesn't work properly with multiple zones.
This is the part that always confuses me, as I routinely use Gizmo, Eos, and JRemote to directly control an instance of MC, and can play back video with zoneswitch and everything switches correctly. I also have special "on-demand" zones outside of mutual stop playback rules, and those also work perfectly. I have experienced no issues with changing zones, zoneswitch, selecting a specific zone, or playing video, provided that I am controlling the given instance of MC directly with Gizmo, Eos, or JRemote (i.e. am logged directly into that instance as a "server").
For example, on one machine I have three mutually exclusive zones, and two special on-demand zones. If I play video to one of the mutually exclusive zones, it winds up in the "video" zone and everything plays nicely. If I instead send content to one of the on-demand zones it plays there instead. I have another machine with three zones, two mutually exclusive, one special purpose, and those also work fine with Gizmo, etc., provided I switch "servers" to control it directly.
I
do get your issues when trying to use DLNA or Tremote for remote control, which is why I generally don't recommend using DLNA for remote control (except when you need to link zones, as it's the only way to do that). When I use Gizmo to log into a given instance/server of MC directly, everything just works exactly as though I were sitting in front of it.
I keep thinking we must be talking past each other somehow, or that we just have vastly different needs/expectations.
No. I don't mind what I use as long as it actually works. Just looking for a tablet solution that's all, which is a remote to a server instance of MC. I keep switching from one technology to the other but I keep coming up against brick walls in one form or another, there's always some design issue or limitation in MC that throws a spanner in the works. (I'm starting to favour DLNA for controlling zones on multiple MC clients around the house becuase you only need to connect to one server and you can see all its DLNA zones. If using any other MC client you also have to set up ALL the clients as servers and then disconnect and reconnect between them in order to control them, because of MC's inability to remotely control another client).
Setting up all the clients only needs to be done once and solves virtually all the problems you're describing above (at least for me). Also try using Gizmo: changing servers is easy in Gizmo because all of the servers are at the bottom of the zones view so switching "servers" is exactly as easy as switching zones. It's one of the reasons I don't use eos or JRemote more, as they make switching servers harder than it needs to be.