What a nightmare coming your way ..Just kidding..

If he is an excellent bass player...don't play bass, left hand or arranger with him..Play two hand piano etc....but I would use the drums...it should help tie you together with him...

When he sings...maybe he should back off the bass and let you play ..left hand bass or arranger bass...

I remember when I started out with a band and I was playing accordion, and we had a real upright bass player that was our singer too...I played mostly the root and fifth as bass and he was able to play the bass lines without too much interference....

Unfortunately on arrangers and left hand bass players...we do more walking and this will destroy another bass player...

Give up the bass to the bass player, play piano and drums..