@audio_phool - About 15 years ago, or so, there was an article in The Absolute Sound, where the reviewer made a pair of speaker cables using a 3 wire, 14-gauge outdoor extension cord from The Home Depot. He used 2 of the 3 wires for the + side and the remaining 1 of the 3 wires for the - side. It caused quite a stir back in the day. I built a pair and used them regularly for temporary use in my system. I never terminated them, just used the bare copper ends, so they were not as convenient as my purpose built speaker cables with BFA style low-mass banana plugs.
Yes, you can build an asymmetric cable and it will sound fine. Of course, you could use the same type of extension cord and just use 2 of the 3 conductors and have a symmetric cable.