In my response, I'm assuming that you mean SSL in your question rather
than SSH, since enable-secure-admin and remote admin are unrelated to SSH.
Nazrul filed an issue about this recently:
http://java.net/jira/browse/GLASSFISH-16690
This issue appears to request exactly what you are asking for, i.e., to
be able to enable remote admin without having to enable SSL. You might
want to watch that issue and vote for it.
Tom