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I don't know if it's simple to create or not, but some motherboard support some functionality to turn computer on or some additional suspend modes (for example Android supports suspend and wait for modem/wifi signal).

Maybe it's a way to create this functionality due to EFI or Core Boot. Of course - I know core boot isn't popular solution, but maybe nerds will use Plasma5 thanks to integration CoreBoot with Plasma5?

Nice thing to have, but it is nothing that a desktop environment should implement. There are solutions for this available for unixoid systems.
Maybe a frontend to control such stuff could make sense, sure, but not an implementation itself.