I don't own DreamScreen, but my new flatscreen is ultra thin on the sides and top, but thicker at the bottom (where all the internal electronics are). This means that, mounted on a wall bracket, the top and side edges are two and a half inches away from the wall, but the bottom rear edge is only one inch away from the wall. Therefore I would expect this to result in brighter light from the bottom where the DreamScreen LED's are much closer to the wall.
In another room, our TV is across a corner, so that one could need the side LED's dimmed.
I would support this. It would be a worthy and useful customization feature, as long as it is not too easy to enable or access. Maybe as an advanced option? It could add a layer of confusion or troubleshooting issues for the regular user when you have a zone that appears to not be working correctly, and it turns out that the brightness was just turned down partway for that zone.
Ideally, we should be able to do this by LED cluster, AND individual LED of a cluster. I have a sharp aqueous TV; on the left edge, there are the power volume and channel buttons that make the TV a bit thicker in this area. Along the bottom right-hand side, there is a part that bumps out a bit, making a TV a bit thicker. It is not always the case where even just a cluster of LED adjustment would be ideal.
I agree with the idea of an advanced zone setting on the app that doesn't confuse simple users, I would even be comfortable dealing with an online interface that connects to my Dreamscreen account (as this is something that I would only set up once and keep the same, probably forever... unless I migrated it to another TV).