17-50 on Pen/Nex will work with right adapter but you can't control aperture, unless you buy a super expensive adapter from conurus/metabones which costs probably price of this lens. But also you wouldn't want to do that coz it can't AF, can do lens correction...the best choice choice for bright zoom is 12-35F2.8? which is supposed to be mid this year.
The few lenses that can achieve pretty good shallow depth of field are Panasonic 20/1.7, 25/1.4, 45/1.8 in order of ranking. By the way, this is not bokeh by the way which is how the lens well renders the out of focus area.
Here's a personal
flickr set on 45/1.8 which is a pretty popular portrait lens, great for kids but you need some space to use this lens.
Btw, don't really understand what you meant by no Autofocus for OMD? A light half depress while video-ing will refocus the subject. Is that what you are looking for?