Route Parameter Validation Problem
My solution was to modify the javascript directing traffic to the mobile video page so that it replaced the slashes with triple underscores.

urlNoProtocol = src.replace(/\//i, "___");

The validation in mobilevideo.routing.yml was updated to vguid: '^[-a-zA-Z0-9._?=]+'

Then in MobileVideoController.php the content() function was updated to reverse the replacement.

$url = preg_replace('/___/','/', $vguid);