I see some no-crack alternatives:
1)If chrome privileges are enabled or they can be reached, then a New File ('/tmp/example') javascript call is all we need. See
http://docs.mandragor.org/files/Misc...-5-sect-5.html
Problem being, I am not sure how fully the js libraries are provided in mozilla minimo (it is minimo). But perhaps they can be provided from any external file.
2)To learn how to build a javascript navigation toolbar *including Save As... button*; this button is disabled in minimo but it should exist. Perhaps toinvoke it does not require chrome priviledges.