Building Balanced XLR Cables

Then tvad they are not balanced. Pin 1 has a shorting contact to the XLR housing. There is no forth ground. The proper wire is three conductor. The forth wire is there I believe for powered microphones. Any interconnect without a proper shield is asking for it.
You hook the shield up to pin one and leave the third wire unused at both ends. You use a floating shield in power cables. You are floating it to prevent ground loops. 

The 4th wire is not for powered microphones.  Powered microphones use what is called "Phantom power".  This is DC voltage that is applied to the signal wires (pins 2 and 3).

The 4th connection on the XLR plug is connected to the equipment chassis/ground.  This can actually be different than Pin 1 signal ground (which is a common/shared ground for the analog circuits), but not necessarily a different connection on all equipment.

Mr. auxinput

XLR should be by STD. No exceptions. Salt and pepper are from another recipe.
I used, built, tested and opened XLR cables. Many for the VOA (Voice of America) projects I was involved (including a winning bid for a station proposal. I wrote book No.4: Audio and time base sub system).
As a part of that rol, we had an Audio expert from the TV broadcast station in Jerusalem. None of your ideas was Kosher.
Powering a mic?
The XLR cables are not for mics. They are for interconnecting home audio equipment.
I would put more attention on the connectors and pick Nutric.
Swiss made, the best in the industry.
Adding a wire (except the shield) is never used in unbalanced (RCA) interconnects, because of the ground loop problem. Why to use it with XLR?