There's nothing to stop you using BNC coax connectors in place of RCA connectors.
The oft quoted 75 ohms is of no relevance - it's not DC resistance. It's 75 ohms impedance, so only of relevance when you're dealing with frequencies far above what's considered to be those of human hearing range.
Radio frequencies.
BNC connectors would give a good, tight connection on interconnects.
A pain in the backside to fit, but a decent audio connector nonetheless.