dual a/b's with common output for a doubleneck

[stompbox steve]

hello
I am thinking of putting  2 a/b's in one box with output B of them going to the same output.
Unsure if this can be done with out massive hum.

Background: I play bass and guitar in a band using a doubleneck.  I want to have an a/b for each neck to send the signal to a common output tuner (tu2).  This will also act as a kill switch for each.
I modified an a/b to show what I am thinking.

http://photobucket.com/albums/y229/stompboxsteve2112/AB%20tuner/?sc=1

There is individual outputs for the doubleneck and there is a neck selector so only one signal will be going to the tuner at a time.  This way I can be playing bass and then mute it for tuning.  No need to have two tuners.

I would be looking at using bi-color leds and power socket not battery.
Please let me know what you think.
Thanks, Steve