While I don't disagree with what you say, I worry about loops of cable are the basic inductor shown in any electrical physics book. It is a small inductor, but it is an inductor.
Coiling wire increases inductance, but coiling cable doesn't, since both wires in the cable produce magnetic flux in opposite directions. That is how non-inductive resistors are woven (bifilar resistors). It is also principle of common mode choke with inductance for common mode signals and zero inductance for normal mode (differential) signals. In addition most of speaker cables' wires are twisted (would be stupid not to) and twisting greatly reduces cable's magnetic field for wavelengths much longer than twist pitch (wavelength at 20kHz is 10km).
As for uneven cables - if you believe that speaker cable affects the sound it will be proportional to length. If it is inaudible to you, then the only think to consider is how hard would it be to sell them in the future.