I can't find a picture of another wheel, rotor-side without the bearing in it, that looks like this. Checked a few part fiches, but they aren't detailed enough... Is this normal? The three protuberances appear much rougher cut than the center circle.
The three "protuberances" are there to positively locate the spacer tube between the bearings, and will not contact it once the axle is in place. It's common in wheels that are made as light as possible and / or where frequent bearing maintenance is expected, such as when racing (the cutouts allow access to the outer race in the event of catastrophic failure).
If it has already been done, it is safe to assume it is possible to do it.
On the other hand, if it has not been done never assume it is impossible to do it.
------- Rob --------