safely narrowing a set of wheels?

[old valet]

I hope I don't get pidgeon-holed on this question; what is the safety or practicallity of finding a set of wheels and having them narrowed? I am quite certain this is not a fantastic idea based on the potential for losing the structural integrity of the 1 piece wheel but I'm curious if it can be done and be as sound as originally built... done by a very qualified person goes without saying. Thoughts?