RCRuiz, I looked at it and it's awesome... very nice
But I don't know if this is a good step in the ui, since there are plans to make blender - engine a plugin, the same with crystalblend. The Blender modeler - animator interface is in combination with game engine already a bit messy - eg in the materials, you can use some features and some not. It' s not bad, because it's much better than doing averything by scripts etc, but my personal opinion is that a single window for (in future external) gameengines might be enough, so the constraint could be better a logic brick. But also the logic bricks should probably not be only the 3 categories which are there now(sensors, controllers, actuators), but a constraint setup could be quite well a Constraint logic brick. Also because sometimes you set/delete constraints dynamically.