Keith wrote:
"Not to mention the difficulties that arise on lines with complex Zo."

Transmission lines are strict enforcers. They only allow a volts to amps
ratio traveling the line of Zo.

Transmission lines are almost always selected and used for low-loss. The
Zo`s which are real (non-reactive) are not complex. The series
resistance is small as compared with te series inductive reactance. The
shunt conductance and dielectric loss are small as compared with
susceptance.

The square root of L/C is a nearly pure resistance and equals Zo, and
equals the square root of Z/Y. Zo is not complex.

The incident and reflected waves are both forced to have a V/I = Zo. In
the case of the reflected wave, the ratio is often written -Zo to
indicate a travel in the direction of the transmitter instead of toward
the load.

Keith also wrote:
"It is a voltage wave which does the travelling."

Sure. That`s why it is called a TEM wave. The E-field is all alone.

Best regards, Richard Harrison, KB5WZI