Hello, maybe with a little JavaScript? Write an extension, which loads your own little module and bind the click event of "#wpSave" (please make sure, if this is the right id for the save button :)). to it. After clicked, add "disabled" or use remove() from jQuery :)
More information for that you can find here:
Load your module with ResourceLoader: https://www.mediawiki.org/wiki/ResourceLoader/Developing_with_ResourceLoader
How to develope an extension: https://www.mediawiki.org/wiki/Manual:Developing_extensions
jQuery is shipped with MediaWiki (i think with SMW, too, but i'm not sure), so you can use jQuery to bind the click event and remove the element.