It's much easier to construct a HD-SDI cable which is only one conductor and shield, maintains its 75 ohm impedance (impedance discontinuities cause signal reflections and inter-symbol interference), and has low loss (larger diameter and air or foam dielectric).
Install Cygwin, it will give you much of the features of eXceed for free, including an Xserver, a local xterm client to connect to your Linux box, and ssh.
Sorry, but it works nothing like you describe.
It is true that there is only one pair of wires involved. Phones (Plain Old Telephone Services P.O.T.S) achieve full duplex with a simple analog circuit called a hybrid. Until the 1980's most phones had no active electronics in them. The hybrid was a specialized transformer which by arrangement of the coils' polarities, the much stronger sending signal is subtracted from the receiving signal in the handset. The subtraction is purposely designed not to be perfect so there is some 'sidetone' left over to give you feedback on how loud to talk.
In modern phones the hybrid is composed of a SLIC (subscriber line interface circuit), basically amplifiers which can do the subtraction operation.
Outside of the phone, both sending and receiving signals share the same pair, just moving in opposite directions.
It sound like this research team just developed a similar hybrid circuit for RF.
Of course you can't flap your arms and fly to the moon. After a while you'd run out of air to push against.