I asked today if it was possible to sit CiviCRM Angular pages (from an extension) at a custom callback relative to CMS root (so, example.org/donate instead of example.org/civicrm/a or example.org/civicrm/contribute/transact?id=1). Have played with a proof of concept for Drupal routing and it's a pretty small addition, but it might need some thought to generalise for other CMS (and if it's Drupal specific you can use a Drupal module to do the same).
In CRM_Utils_Hook we add a new hook, eg hook_civicrm_alterRoutes -
In civicrm.module we introduce the hook civicrm_menu().
In the extension we can activate CiviCRM (and subpages!) by fiddling a little.
Hope the formatting in this ticket worked.
(I can PR this, but it's just an idea atm. It works for me currently to activate Angular code at an alternate URL which doesn't have the civicrm prefix, with no other tweaks required apparently.)