Dream connector, but still grounded in practical reality? hmm...
Probably Outokumpu 6 nines Upcast copper meant for super conducting applications like particle accelerators.
If it's good enough to pass the quantum mechanics requirements of particle accelerators, I think it's good enough for me
http://www.outokumpu.com/files/OUTOKUMPU%20English%20(May2002).pdf
As for geometry, that's a little tricky.
Perhaps twisted for reduced EMI susceptibility.
For dielectric, someting like Eccostock PP (lower dissipation, lower dielectric constant than teflon)
http://www.eccosorb.com/catalog/eccostock/index.asp
Shielding is a bit of a problem. You put a shield, you get less RFI, but get more capacitance, which people claim is detrimental to sound.
Something like the above could be a starting point.