I'd love to see him in some of ambassador role. He clearly loves the club and "gets" us. Brilliant player for the club, what I'd give to see him and Arteta in their primes playing for us now.
Get him in pre-season for some coaching in being snide. Just getting into the spirit of Big Sam's Everton. Perhaps a well-publicised motivational message pre-derby alluding to in-your-face tactics. Just to rile the rs up. Can you imagine Klopp's Coconut rolling around on the floor after that match if that came off.
As brilliant as Cahill is/was, he's had his time with us. To be honest, I think he's more interested in the continuing development of the 'Cahill' brand.