transparancy buttons

I am messing around, with transparent buttons.

On mac they look better, transparant, but on windows we use the Kunstoff L&F and than transparancy does not look nice.

What I wanted to do is set the transparancy by scripting (changing the css)
But we can’t use transparency in our css. :-(

Is there any change that that feature could be implemented in future release?
or is it a java-issue?