good point calmac1991. I don't know anyone who's tried this, but without electrical assistance the focus is disabled on Zuiko lenses, from what I've read. You could however use OM or other lenses that don't depend on the electrical input and focus manually.
That is correct, focus by wire from the digital Zuiko´s requires the EX-25 to make it work.
I actually just bought the OM Zuiko 50mm 3.5 macro (to use on OM Bellows), but first impression is that it is almost as sharp as my digital Zuiko 50mm macro. And with the OM Zuiko you can focus and set the aperture manually and use very simple extension tubes.