Is it possible to replace page arguments with new ones in a view exposed filter?
You can adjust the default Filter identifier for each Exposed Filter in its settings. The Description: 


  Filter identifier
  _
  This will appear in the URL after the ? to identify this filter. Cannot be blank. Only letters, digits and the dot ("."), hyphen ("-"), underscore ("_"), and tilde ("~") characters are allowed. 


In your case you can chage the first one to geo and the other to _. That way you get the output: 

cities?geo=2&amp;_=4

although you'd probably name the second one to something more meaningful, like region: 

cities?geo=2&amp;region=4

For full control use the module Query Parameters To URL (Drupal 8 version Needs work).