If I was to have a stereo delay and a stereo reverb and run the wet signals to an ABY box, could I Y those signals into a harmonizer/pitch shifter and then run that mono signal to an ABY box with the dry signal and make it go back to a mono signal to go straight to my amp?

Sounds confusing, I know.
Er...what were you hoping that would do for you?
It wouldn't really do anything different than running them in mono the way I'm understanding it.
Keep the original signal the way it is, but be able to have harmonies in my delayed repeats and reverbs.
Oh, I see now. Yes, I suppose that would be possible. Might sound strange, but it would work.
Actually, you'd need a different setup. What you'd need to do is get a Y cable and run the wet output from both reverb and delay into the input of the harmonizer. From there you'd need to run that output into an A/B/Y with the dry outputs of those pedals (they could be in series) and then to the amp.