I'm planning to build an online component for my computer game and am wondering how much DNN can help.  It's not an MMO or anything, basically just high scores.  Here's my dream scenario:

-User hits the website and decides to buy the game
-They create an account on the site
-they buy the game through an integrated (not sent to another site) payment gateway (maybe Paypal Pro or AuthorizeNet)
-After purchase, the "My Games" area of the site allows them to download the game whenever they want to (if logged in).

I think DNN can handle all of that.  Does it have any protection to prevent someone from sharing their download account too much?

Here's where it gets harder:
-The user installs the game and runs it
-From the game, they're asked for the username/password they used on the website
-If authenticated, they're signed in to the online portion of the game.  Otherwise they have to play in offline mode.
-After completing each level their score is submitted to the site with their username.  The relevant high score table is sent in response.
-They're booted from online play if someone signs in from another computer with the same account.

Of course the high score storage and presentation will have to be a custom module.  Do you think this will be fairly straightforward with DNN?  Maintaining a player's game session is probably the hardest part.  Booting off a player can occur as a response to their next server request (probably fetching a high score table) - it doesn't need to happen immediately.

I'm looking at various CMS systems since I'd like the store, forum, and high score system all tied to a single account.  Do you think DNN is a good choice to build this from?  What do you think will be the biggest challenges?

Thanks for your help!