>> Yes, I think I like it. But it is very dubious: it means that it is 
>> easy to make stupid spelling mistakes when creating the class, 
>> resulting in a namespace being created without me knowing it (see 
>> further).

> We could add a little "confirm". :)

Please, no.  And, in those other areas of Namespace conflicts please, can we
take the less-intrusive approach.  That is, like Monticello "Merge" followed by
"Load" if you like what you saw with Merge.

Warnings and confirmations are the computer driving the user, not vice-versa. 
Ward Cunningham approach is to provide "corrective" facilities for human error.

BTW, I think I *really* *really* like your proposal!  At least the major points
of it meet my requirements (optimistic, optional, etc.).

Regards,
  Chris