@ksaj @glitzersachen @loke @amszmidt
I was going to point out that you could print your Roman numeral to a string, then use read-from-string to get it back with a different *base* setting, and put that into a defformat definition to extend format, and...
... and then I remembered that (a) defformat isn't part of CL, and (b) even if it were, that way lies madness.
So, yeah.
I guess I'm with you, once I calm down enough. :-)