Not sure how you would be able to provide the shielding which is necessary for an interconnect, or how you would connect the heavy gauge speaker wire to an rca connector. Also, low capacitance can be important in an interconnect, depending on length and on the output impedance of the component which drives the cable, but the speaker cable might very conceivably have capacitance which is high and/or unspecified.
Regards,
-- Al
Regards,
-- Al