I'm not sure if it's possible to separate "felt intensity" from "intensity of desire". (I don't know what pain/suffering without a desire that it not exist would be.) But however that may be, your point doesn't seem to settle the population-ethical issue: If we look at hedonic desires (weighted by intensity), should we maximize [fulfilled desires - unfulfilled desires] or minimize [unfulfilled desires]? A desire can be considered a problem to be solved. If we want to solve the world's problems (which motivation seems to underly what many people are doing), does it make more sense to minimize unsolved problems or to create as many solved problems as possible? - I think clearly the former, for the non-existence of problems (and thus of solved problems) does not intrinsically pose a problem.

Why isn't it all one scale of "felt hedonic intensity"? If it was all one scale, it seems that placing the 0-point would be a purely formal and arbitrary matter. But we agree that it's not - so there seems to be something substantial going on when hedonic tone changes from "pleasurable" to "painful". We're not sliding along a scale of more/less of the same thing - at some point, the thing in question changes. Suppose I grant you that there is a way of comparing pleasure- and pain-intensities: "Here's a pain of intensity x, and there's something that's a pleasure and has the same intensity x." Now how are you going to establish that x-intensity of that other thing (pleasure) morally outweighs x-intensity of pain? Maybe it's 2x-intensity of the other thing? How's that choice not arbitrary? As Lukas said, the choice seems to be based on how much you crave the other thing (and its greater intensity), i.e. on how much of a problem its absence is to you. And this brings us back to minimizing unsolved problems, it seems.