JOSM Upload a layer modified outside of JOSM

I have used this Overpass query to download all the highways of a given city (indicated by XXXXXX) that have the tag name. The data was saved into a file.

<osm-script output="xml">
  <id-query {{nominatimArea:XXXXXX}} into="area"/>
  <query type="way">
    <has-kv k="highway"/>
    <has-kv k="name"/>
    <area-query from="area"/>
  </query>
  <union>
    <item />
      <recurse type="way-node"/>   
  </union>
  <print mode="meta" />
</osm-script>

Outside of JOSM, with a very smart script, I've parsed the OSM file to check if the highway's names were correct: if not, the script change them to the correct values. Keep in mind that I know exactly which way (hence its ID) is going to be modified. When the edit is done, I would like to upload the file to OSM through JOSM: if I click the Upload button, JOSM tells me "No changes to upload".

So far I thought about two possibilities:

1. Download the area of the edit, then load my layer, and finally merge them. Then upload. Though, this is not feasible for me because I'm working on entire cities: the data to download would be too large.
2. Obviously JOSM is able to detect the changes to a layer. Is there any tag I can add to the modified ways in order to get JOSM to upload them?

If you have any other suggestions, please keep them coming. Thanks.