Late to this discussion, but it is intriguing as I spoke with my 'possible' doubles partner for our tri-level team last night about this. We're both 4.5s, but he smacks the ball much harder than I do (imagine the pairing of del Potro & Ferrer).
We can both return well from both sides, but my ad return is pretty much automatic, no matter the serve. I feel that this gives him the ability to 'swing away' at his return, knowing 90% of the time, I will give us a good opportunity to win the point on my side.
Of course, it helps that (1) he's solid at the net, and (2) is 6' 4" and has the wingspan of a pterodactyl, but still, it is my feeling that having the solid returner on the ad side *can* free up the other person mentally, allowing them to take a crack at the ball with minimal negative effect. You just need to let them know you are OK w/ them taking a crack at it.
"No worries, I'll give you another shot"...