Being able to have photos' EXIF data be "right" for old, converted lenses would be really cool, both for chipped and unchipped conversions.
For unchipped lenses, it should be easy to detect that there's no info coming from the lens, because there'd be nothing there. In this basic case, it'd be nice to have the Aperture value be the value from the camera (set by the user in Aperture Priority or Manual mode), instead of just empty.
Next would be to have files on the card that would hold the values for the particular lenses that the user wants to choose from. Then expose those in the menu system somehow so the user could choose among a set of lenses to have the EXIF data be right for MaxAperture, FocalLength and whichever EXIF field has the name of the lens.
This should be smart and only do this manipulation when it detects a chipless lens (so there's nothing to do when using a regular Canon lens).
For chipped lenses, it would get a bit trickier, but it should be possible to do some sort of autodetection based on the results coming back from the adapter. Some mix of FocalLength Xmm and MaxAperture Y and lens name "1234" would mean use the Takumar 50mm f1/.4 preset (or whatever).
Being able to create or modify the presets from right on the camera would be a bonus.
Plus, with the original poster's idea of modifying the camera name would cause Magic Lantern to show up on Flikr and other sites, which would be pretty cool.
Is any of this even possible?