TRS to Dual Mono box with phase flip option?

[aab0mb]

http://www.geofex.com/Article_Folders/polarity_reverser/polarity_reverser.htm

If i was running a TRS to dual mono and wanted to have control over phase on one or both sides, would i be ok in setting up a dual op amp and duplicating the above circuit to be applied to each mono line? I'd like to fit this in a 1590b box if possible so component count is a consideration.

Would there be any special considerations one should make in setting up such a device with regard to power, LED indicators for phase, and so on?

[PRR]

The only real gotcha with that plan is it is a bit low-impedance and high-hiss to use direct from a guitar.

[aab0mb]

What would be the best practice approach for such a device? TRS to dual mono with the ability to flip phase on at least one of the mono lines? Buffered mono lines aren't essential but would be nice to have.