This is one of the limitations of multiple sites on SharePoint and publishing separately to each one. You can use a content type and then just update the one version but you'll still have to change the sites to use that content type. Should be easier going forward though. However, if you are hard-coding the submit location, the single content type won't work. Why are you hardcoding submit?
You don't necessarily need to do this. You could use Save and just have users save it to the library. You could also add a secondary XML data source (with UDCX) that filters save location based on some criteria and uses a little code or Qdabra's qRules (Qdabra pays for this free site) to submit to the filtered URL.
To batch deploy multiple XSNs (not the content type approach) you can look at the STSADM command that comes with the SharePoint tools. It programmatically publish XSNs but you'd still have to fix them up to point to have the SharePoint submit adapters point to the right locations.
In general, publishing to each site is a bad practice. Using a content type or a single XSN location that submits XMLs to different locations is the best practice.
Good luck!