I think may already be possible using Zigbee and the Zigbee Hub Pro.
What made me think of it is your mention of copying scenes overloading your servers.
Make scenes run on our servers. It does not take much to serve simple internet like wifi routers do. I am guessing eWeLink Web and dashboards connect centrally rather than on the local network, but the devices running them have memory. Also the NS Panel Pro is quite clever I think; is it android? Also if home Assistant is connected to eWeLink you have access to memory in the computer running it.
Many (?all) of your current switches have a local mode? If you download the scenes to the computer running eWeLink Web, Dashboard, Home-Assistant or the NS-Panel-Pro you could save your server working and allow us to copy scenes. You’d probably want a back-up in case everything local went off-line but actually running the scenes could be local.
Also an old phone running the camera could do it?