I completely agree with you on the fact that Mac4Lin doesn't bring 100% Mac OS X UI to Linux.
When you ask "Can't xyz be done?" from a user's perspective, I'd say you are not wrong in asking that. Me, being one who codes themes can answer this question from a coder's perspective. Different themes give different levels of accuracy. Each component in a theme is tightly integrated. So to get that certain "abc" you may need to implement the theme in a certain fashion. This means, if you haf "abc" in your theme you may not be able to implement feature "def".
But yes, with the latest versions of engines it maybe possible to integrate all features. I did try a couple of what you've indicated in your screenshots, but unfortunately it broke the existing elements. Surely, working hard on the current code, I suppose we can achieve the results. We'll prolly haf to re-code all the dependent elements.
I do not rule out including all this in the next version. I will try whatever I can with the limited time I haf.