This would be quite hard to implement practical and universal.
SFML is used in a lot of different enviroments with a lot of different window handlers. Think of it, there is no "global" way of making a box on them all. Each system has to have a hand written implemention, not to mention the intergration with QT and such.
And then also, this would distract the focus from a simple and fast multimedia layer and turn into something bloated. There is no universal way for each project. I know people using it for games, visualising studies and such.
Get developing with Win32 or QT is my advice.