If #3057 would be merged we should provide way inject some parameters from configuration. For example we have mobile version of site and desktop.

hostbased_route:
  pattern:  /
  requirements:
    _host: site.com|m.site.com

Each developer has local copies of site (site.dev, m.site.dev). There are also test version of site (site.dev.mycompany.com, m.site.dev.mycompany.com). So right way move this hostnames into parameters.ini wich separate to each deployment

hostbased_route:
  pattern:  /
  requirements:
    _host: %site_hostname%|%site_mobile_hostname%