I think there are plenty of drip system designs and automatic water chaning systems out there... not exclusive for discus use. I've seen many members mention they have semi-autonomous system here.
I myself have a rough semi-auto one. Flip a switch to turn-on pump to drain, but I still have to turn water on and turn it off. I'm working on a system to turn a solenoid valve on/off but I'm too busy to work out the details right now. There are plenty of people who do it though and if you can't find it here, you can google it.
Changing water is only one part of it though. You also want to siphon debris out... don't think there is a system for that, but you could always keep pretty good water flow directed at the tank bottom to lift junk up for the filters and pump to pick it up.
I have a siphon tube-to-drain.