Using the domcfg we can map another change password form, however other change password trigger such as Force user to change internet password on next login, could still use the default ?ChangePassword form command generally used by Domino.
Apparently the ?ChangePassword command is a form related command executed by the Webserver. Even a different form is defined it just pulls the forms design, like fields, pictures, etc. and processes the input request. There is no support for modified Save buttons or Webtriggered agent at this stage. This is the reason why even if the form is defined in the Webserver Configuration, only a supported design features of the ?ChangePassword command are used.
And redirections to a different database via Web Site Rule on the other hand, like URL substitution, would not work for the ?ChangePassword command as well.
Requesting for another approach in enforcing usage of another custom change password form, other than the workaround of copying and pasting that custom change password form onto domcfg and renaming it to $$ChangePassword to compel it into using that.