Hi Friksel, nod74,
This was indeed being worked/fixed at the time of the post (it's being tested as we speak). The fix will be included in v1.8 Beta for Mac (not released yet) and (then) on Windows (the current Windows 1.8 Beta doesn't include this fix). Some issues imply rewriting parts of the code or the whole feature - they are not just simple corrections or addons to existing code and take more time and testing than usual. With Publisher's recent release a lot of time and effort was spent on solving its issues and on its integration with the rest of the suite which ended up delaying Designer and Photo 1.8 Betas a bit. As explained several times we have limited dev resources and some fixes may end up taking more time than we hoped for but that doesn't mean we don't care about customer's issues/problems. We are simply doing our best with the resources we have. Thanks for understanding.
From what I know there is a method that can work for you:
1 - Select the strokes you want to expand and in the Stroke panel check "Scale with object"
2 - Increase the size of the icons (for example from 50px x 50px to 1000px x 1000px)
3 - Expand strokes
4 - Scale back the icons to their original size.