The switches don’t have to control the lights they are wired to. I have Inovelli z-wave switches, and on these you can disable the relay. So the switch can still send out commands/scenes on the network but the relay is always on.
Then you would put in a relay unit in the electrical box of the lights or if you have enough room in with the switches. Then setup the switches to control their respective sets of lights.
Might even be a switch out there that lets you disconnect the relay from the buttons on the switch but still control the relay which would cut down on the device count.
In any KDE app you can connect with SFTP in the open file dialog. Just type sftp://user@server/path and you can browse/open/edit files the remote server. ssh keys+agent make things a lot easier here obviously.