Don't need to imagine. These guys are doing it.
They're running it off a Raspberry Pi module
using Linux as the OS.
Yeah, it's been done before. They already have open source growing software made just for this on GitHub. I read about it before. Still cool though. I don't think it's that popular because it's a lot of work for stuff that already exists. Now for a commercial grow, yeah a brain box would be a game changer.
But I don't have anything else that needs a controller. And I kind of like having my controllers separate. I don't need to water anything with the hydro setup I have. Just topping off the reservoir is all I have to manually check, until I have a room with a water source so I could automate that.
Ph controller for ph drifting, temp controller for exhaust fan/humidifier, dehumidifier has built in controller, and then mechanical timer for lights. I don't know what else I could automate besides having something drop nutes in, but if I only have to do it every two weeks, that doesn't save me a lot of time. It would be more time dialing it in than current process of actually doing the labor.
Of course that's my opinion.