If you were omitting the spool at the top, you could just add your additional 1/2" to the width of the white fabric there, and cut the white side piece a 1/2" longer too.
If I was going to keep the spool, I would add a 1/2" to the pieces in the center, in the throat area of the machine. Add a 1/2" to the 2 white pieces, the purple square, and the white strip on the side. I don't think that would compromise the look of the block.