Could you consider adding a "hook" which calls an optional user-supplied PHP function
which would allow a re-write of the URL string, and use the resulting string as the output
into the sitemap?
I would like my sitemaps to contain SE "friendlier" forms, instead of the parameter-ful
forms found my traversing the site. A display-form post-processing function would
allow that, as in the way a ".htaccess" rewrite might do.