I don't think Lowry, ibaka and Fields will be as productive without a plethora of better scorers around them. You have 3 4th options in your staring 5. That's my big objection.
So you're saying they'd be less effective if they take more shots?
You might be right...its pretty difficult to say. They're all young though, and considering Fields' consistency, Ibaka's incredible improvement in only 1 year, and Lowry's improvement from last year to this year, especially in scoring..I think it is just as feasible that they'd be able to maintain their current efficacy, and possibly (I'd say most likely in the case of Ibaka) improve on their impact further.
The biggest concern I think is actually Paul Pierce. Although all 5 starters project to be 10 ppg scorers, Paul Pierce is a significantly worse player when he tries to be a hero for a whole game. If his FGA's go up significantly, I think his FG% drops just as significantly...so it will be important that some of these guys come through.
I'm saying they won't receive as quality looks as they do know and be forced to play against the more stringent aspects of a defense.
I don't see it that way, but I guess that could be explained away because everyone loves their own team.
I am confident that Pierce and Bogut will give other teams a fair amount of trouble, and I don't think the quality of open looks will decrease all that significantly for the trio of Fields/Lowry/Ibaka. On top of that I'm confident that Lowry, Fields, and Ibaka have all not only proved they're able rotation players for good teams, they've also got room to grow.
I don't think that scoring will be as big a problem, partially because I think you're underestimating how good my supporting cast can be, but also because I think the defense will make scoring less of do or die factor in the outcome of games.