I could see having the minimize and a zoom button on the left and the close button on the right, it would look sort of like MacOS classic. It is a decent idea worth exploring. I am not saying that it is a good idea, just that it might not be a terrible one. There is no point in debating which is a better UI choice from a design perspective, double click to minimize or having a dedicated button for the task, it is all just personal preference. I got used to double-click to minimize, I could get used to a minimize button. Changing the window bar would be an uphill battle because it is one of the "holy cows" of Haiku that shall not be altered without great trepidation. Inertia, I fear, will kill this idea before it ever has a chance.