Ray won't have to come off walls of screens to get open in Miami. When they run their offense through Lebron as LeBron is set up in the low post with Wade at the top of the key it opens up all sorts of wide open looks for players on the three point line in the corners and at the foul line extended areas of the floor.
All Ray will have to do is stand in one of those areas and when the double team comes to LeBron in the post or Wade at the top of the key after Lebron passes it to Wade, wait to get the wide open shot.
All true, but it is still a diminishing role for Ray, one which the ball will be in his hands less, not more. Doc didn't say Ray was clamoring for more spot up shooting opportunities, he said he wanted more pick and roll chances, i.e. getting to initiate the play with the ball in his hand. I doubt he gets a single opportunity to play that way in Miami.
Yeah I don't get this notion that Ray is going to be thrilled with the role of standing in the corner waiting for Lebron or Wade ti possibly throw him the ball for an open shot. And how many shots is Ray realistically even going to get a game? I highly doubt more than he didnin Boston
Heres the other thing.. If im the head coach of any NBA team and ray is on the floor im telling his man to never double team lebron or wade no matter what. I'd send any other player to collapse on those two, but knowing the three ball is coming from Ray i'd always keep his man glued to him. Seems pretty self evident to me too. That's his strength, why feed into it? at the end of the day, a three is still worth more than a two. With way less screens and movement away from the ball ray can be easily neutralized.
Well, that of course presumes your guys can defend Lebron without doubling him.
But yeah, I mean, this was the same value that Ray Allen provided the Celtics - teams can't afford to leave a 3PT shooter who can shoot over 40% alone. So Ray would drag some shmoe all over the court and away from the paint, helping to open things up for Pierce, KG & Rondo.
Whether he moves through screens or rotates to spots along the perimeter, he's going to provide the same kind of threat for the Heat.
The way you neutralize is either by defending everyone straight up - no doubling. If you can't do that then with defenders who can help and then still recover fast enough to contest his shot without fouling.
The main point i was trying to make was just leave rays guy on him no matter what. Never use that man for the double team, and make that be the rule. In other words, don't cheat off of ray no matter the situation. Keep his guy glued to him. The heat will be far less likely to actually run ray through screens and make him be the focal point of their offense, so if that's the case he has a real hard time shedding his man. We've all seen that here first hand for about two seasons now. As others have said his ball handling abilities seem to have decreased as has his mobility and speed. His game is dependent on those things to get him open looks. I can see him becoming very frustrated and creating more drama the less effective he becomes. His bloated self importance and reluctance to see his diminishing game as age conspires against him could really play into our hands. That's my hope at least. 
Yeah but if you do that then how do you defend Lebron in the low post? One on one? LeBron will eat everyone up if you do that.
If you double off Wade, that's foolish. You may as well just give the Heat 2 points and put Wade on the line for an "and one".
So your only choice, if you are going to double Lebron and Wade, depending on who has the ball, and leave single coverage on Ray is to double off Mike Miller, Shane Battier, Chris Bosh, James Jones or Mario Chalmers, depending on who is in the game. Bosh is deadly from 15 ft and in and a bad double off. Miller, Chalmers and Battier are all very good three point shooters too. Miller shot 45% from three last year. Battier has shot over 39% from three in four separate seasons. Chalmers improved to almost 39% from three last year. Jones has shot over 40% from three for his career.
Ray's role will be significant because of what it means to floor spacing for Miami and how far they can spread defenses opening holes for LeBron and Wade while leaving excellent three point shooters wide open.