The furniture dialog might become too big, no?

Maybe, but is useful.
Could be used after we decide to show the name in plan by popup the same text and style dialog or in the context menu on "Modifies text and style..." after we create the furniture.
Also could be an icon in toolbar for chose the color of text.
Until this I'm happy to insert separate text box but I can't group it with a furniture to move it together.
Anyway You've made a great program and become greater.
Congratulation!