I would challenge the idea that having to double tap for everything is only a minor inconvenience to the user. Tapping (or clicking) if the most often used interaction (Yes I am making an assumption here). Having to double tap makes me work that much harder every day to accomplish my tasks.
An important statement "It would give designers far more flexibility and power" I have to greatly disagree with. We, the designers are making products for them, not us. There are lots of things we can do as designers that would give us more flexibility, power, job satisfaction, etc. that would make the users life harder. We need to be looking at ways to accomplish things that make their life easier first.
There are other side effects to your proposition. Taking away double tap removes the ability to double click something and effect a different action, like it does on the desktop, like click to select vs double click to open. Mobile apps sadly lack the ability to do things like multi-select without the help of an edit mode which requires this kind of interaction. Hopefully this will begin to change, just as web apps have taken many things from the desktop over the years.
Touch interactions for mobile have started off very simple. Everything is single tap. I look forward to the touch interactions growing up to include some more robust interactions we as users are already used to, but I think tapping to hover, double tapping to click is in the wrong direction.
Just my opinion...