I know how to change the MIME type in a webserver. I used this to make sure the browser downloads my .scrpt file instead of opening the plain text version. So far so good bu
You can specify a type attribute, but the content-type sent by the server is authoritative.
This attribute gives an advisory hint as to the content type of the content available at the link target address. It allows user agents to opt to use a fallback mechanism rather than fetch the content if they are advised that they will get content in a content type they do not support.
Other than that, no, you can't.