Is it possible to rename standard related list button without replacing standard new button with a new custom url hack button ?
No, you cannot rename the standard buttons. You'll have to create a new button then uncheck the new button from the related list buttons.
To create the url hack a tutorial I found is here: http://raydehler.com/cloud/clod/salesforce-url-hacking-to-prepopulate-fields-on-a-standard-page-layout.html
By using a relative link you can remove the first part of the link https://na1.salesforce.com and jsut start with / so it will be dynamic to whatever environment you are in. Also, comes in handy if your org gets mirgrated to a different pod.
Please vote for this idea to rename standard buttons