If it's the same midi track... there's no benefit to doing it that way.
the 3 tracks will be louder due to the cumulative nature of the audio.... but you will not have any meaningful advantage.
Simply bounce it down the center. Then you can pan it right, center, left or any point you wish.
Doing it that way simply gives you 3 tracks with the same exact audio data and that equates to MONO. Unless the piano output is a STEREO piano, and has different audio info in the 2 stereo tracks..... you will end up with mono no matter what you do.... assuming the same midi track powers the audio tracks.
The better solution would be to have a different instrument..... maybe an acoustic guitar and pan it opposite of the piano....and keep them both at maybe 20% panned from center. Or a nice B3 organ sample/patch..... That puts a balancing instrument on the other side and gives you some degree of stereo separation in the sound stage.
I have experimented doing what you describe, and I always came back to one track...centered. I tried several different things to make that piano sound bigger and better..... inverting phase..... off set the tracks with nudge..... reverbs on some.....
nothing was as satisfying as a nice clean piano in the center where I could place it where it was needed.
By all means experiment and try things.... that's how you learn and who knows... you might find something that works in a given song situation.