Impractical, whimsical, the possibilities are endless. I have attached pix of three Franken-Camera set ups. Size-wise the C/V 35/1.4, 40/1.4 and earlier screw mount lenses balance well on the camera. But so many combinations are possible. Now, it we could just get a camera with a FF sensor to adopt this sort of flange-to-sensor register. They'd sell like hotcakes.
Below are the E-P2 with 1) a Pentax 67 55mm/f:3.5 lens (Pentax 67-to-Nikon, Nikon-to-4/3 adpapters [silly, but quite the performer -- see pic below]; 2) Pentax 35/f:2 M42 and extension tube and 3) Leitz 35/3.5 Summaron w/eyes (eyes just for show at this point . . .).
And finally the rainy-day image of a rose taken with the Pentax 67 55mm lens:
Mabelsound, if you follow the links in jackslai's post to his flickr page, you will see a step-by-step of how he adapted the Yashica lens. Yikes! Pretty impressive, especially considering the stellar results, and not for the faint of heart.
Now, those cine lenses look pretty sweet . . .
[Edit: Here's one more from the same rainy-day Franekn-camera shootout. E-P2, 35/2 Pentax M42 mount and extension tube, converted to B&W in CS5 and the reds dialed down. Thew 35mm lens was wide open at f:2 - the central rose was white and the surrounding roses red and peach colored.]