You will only need the outer two wires if you are just pulling pack voltage and not actually using the "balance" functionality.
If you intend to install the vTX semi-permanently on the model, I would suggest just soldering in an extra power lead (using the vTX's power plug) from your ESC's main battery connection. Or if this is a multirotor, pull the pack voltage off of your power distribution board. That way you aren't constantly having to plug/un-plug the balance connector when you fly.
I've frequently used these to plug in an airframe's auxiliary circuits (lights, FPV . . . whatever) that I don't want "always on"
Cut off a 4 pin length, solder ground to one side and power to the other, then give a shot of hot glue on the backside to cover the solder joints and give a litttle stress relief.
When I'm ready to use it, plug it into the balance plug.
I will caution, some FPV gear won't like plugging it in backwards (some don't care and LEDs for lights just fail to come on). If you put a diode in-line with the positive lead, it'll break the circuit if you plug it in backwards, and most FPV gear won't care about the 0.5v - 1v drop across the diode.
I'd also caution . . . be prepared to add a power filter between the plug and your gear. You *can* run off the same battery, but power noise from the ESCs can leak into the video signal. This, of course, wil depend on your gear, but if you see the interference in the signal increase as you power up the motor, then you're loosing range to noise from your motors. Either a filter or a small battery are easy fixes this issue.