VPTK is a wonderful WYSIWYG. It's written in Perl and it's free. It works both on Win32 and X$. Check this out along with other tools and scripts at: http://www.perltk.org/ex/index.htm.
I've been playing with Komodo, by Active State lately. It has a GUI which uses the GRID geometry. No Pack or place! It's not bad either.
I think implementing a WYSIWYG editor for pack() is very hard. And place() should not be used at all, only in very special circumstances using relative values or for quick'n'dirty scripts.