Geert Vancompernolle wrote:
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Question: is this feasible? I'm thinking about the possibility of cross talk, the impedance, the power (current), length, frequency range (although only max. 20 kHz),...
Are such type of cables suited for that purpose?

1.) WAAAAAY off topic.
2.) I doubt you can get away with it. The voltage drops will probably kill you. I'd try low source impedance audio signal distribution and satellite power amps.
3.) There are on-line forums for Home automation that will help enormously.

Steve