I recommend that you check out my blog:
SAP GUI for Windows 7.60 will come with a Belize theme for all SAP products (with a reduced feature set).
I guess this is what you are looking for.
As far as i've understood it, the personas service can utilize a fiori like (belize) theme.
Personas is in charge of rendering the web-gui.
For more details check: http://www.kodyaz.com/sap-abap/enable-belize-theme-for-sap-screen-personas-on-web-gui.aspx