What it's the easiest way to add a flash frontpage without alter Views node page?
Try using Themekey if its a different look and feel altogether... or Frontpage. Although you can create a node and have that node set as the frontpage in the sites configuration page. You have to use jQuery to have the page render the flash in drupal. As for redirection, what you will have to do is create a jQuery or actionscript that gets redirected at the end of the presentation or use the rule module that gets the page redirected after your particular condition is met. That is what I used on a previous project.