You can make it....but at the end of the day you won't be able to integrate it to the PSN or XLive or Activision, so it won't be able to fetch data.

You would've accomplish nothing but a waste of time.

-There is one solution though. Dualboot NiTDroid on your N900 and access the official CoD app by using Android.
-If that doesn't work (because of crash or no internet network) I suggest having a look at WebOS and seeing if HP/Palm devices have the same official CoD App. They probably don't but if they do, then try it on the N900 using Preenv.

BTW WM2 was better than MW3