I'm sorry to say it but you don't sound like someone who has used Drupal for long at all. First, Drupal isn't a CRM. It's a framework that includes a CMS. For a great CRM that integrates with Drupal, take a look at CiviCRM (http://civicrm.org).
Second, what you say about making modules work consistently doesn't make sense to me, at least not as you describe it. Drupal can be hell on earth sometimes, but it's the job of the developer to decide which third-party modules fit the needs of the project and what needs to be written from scratch. Besides, audio and video attachments are usually wrapped in a Flash player and that depends very little on what module you use.
It also seems that you aren't aware of the best practice (http://drupal.org/best-practices) of not modifying Drupal's core files in order to "customize" your site. Of course modifying Drupal will make it hard to upgrade! Instead of creating a somewhat versionless fork of Drupal you should be using custom modules or PHPtemplate overrides to achieve the functionality you want.
Second, what you say about making modules work consistently doesn't make sense to me, at least not as you describe it. Drupal can be hell on earth sometimes, but it's the job of the developer to decide which third-party modules fit the needs of the project and what needs to be written from scratch. Besides, audio and video attachments are usually wrapped in a Flash player and that depends very little on what module you use.
It also seems that you aren't aware of the best practice (http://drupal.org/best-practices) of not modifying Drupal's core files in order to "customize" your site. Of course modifying Drupal will make it hard to upgrade! Instead of creating a somewhat versionless fork of Drupal you should be using custom modules or PHPtemplate overrides to achieve the functionality you want.