QProxyModel is dangerous, because it maps indices without mapping their positions. I can't see the parallell to QProxyModel from QGraphicsTextItem, could you explain?

QGraphicsTextItem is just as powerful as QTextEdit, but it's a graphics item. You have complete QTextDocument access. I understand from your first post that you want a way to remove the focus rectangle, and you found a way. What other limitations have you run into? I understand that you want QTextControl to be public, but I don't understand why. ;-)