All I am suggesting is that interfaces should be used to promote the usage of XML in general and topic maps in particular, without annoying users with information that is both unwanted and unnecessary to the task at hand. I am just not certain that I would choose ISO 13250 over XTM simply because I had a difficult interface for users. The more obvious solution, to me at any rate, would be to create a better user interface, whichever standard, ISO 13250 or XTM that was chosen for the task at hand. This is the argument that the W3C uses to sell Schema too. Users will never have to look at the underlying syntax.
Users range from the data entry clerks and subject matter specialists to the topic map creators.
Been there done that. I'm with Martin - keep it simple for the humans to do in the first place. Martins point that we can't be limited to a single set of rigid tagsets. The existence of a single underlying tagset in XTM has no impact on what is displayed to the user. What is displayed to the user is the choice of the interface designer.