Venous:
The file I linked to contains the stuff that lets the Hat switch work. If you downloaded it, those files should create two JoytoKey "profiles" that should work. I've been using it so long that I forget what it actually does, sorry. You can do it manually, just follow the steps below.
Download JoytoKey. After that, open the program and hit the "Create" button at the bottom. Name it whatever you want (mine is named BF2). Go to "Preferences" on the right and hit the checkbox that says "Use POV Switches." Click "Joysticks" on the right to bring you back to the right tab. Now, right click on "POV1:UP" and select "Configure this button." Hit the "Keyboard" tab at the top if it isn't selected. Click on the first box marked "Disabled" and it should turn yellow. Now hit whatever key is your "Mouselook" key in BF2 (default Left Ctrl). Then hit OK. Repeat for POV1:DOWN, POV1:LEFT, and POV1:RIGHT. Make them all your "Mouselook" key. It should look like this:
Now, hit the "Create" button again and name it whatever you want (mine is BF2a). Enable the POV Switches in "Preferences" again if they aren't. Now Configure "POV1:UP." Switch it over to the "Mouse" tab in the configure window. Slide the Vertical "Cursor Movement" Slider all the way up. Hit okay. Now Configure "POV1:DOWN." Switch it over to the "Mouse" tab in the configure window. Slide the Vertical "Cursor Movement" Slider all the way down. Hit okay. Now Configure "POV1:LEFT." Switch it over to the "Mouse" tab in the configure window. Slide the Horizontal "Cursor Movement" Slider all the way left. Hit okay. Now Configure "POV1:RIGHT." Switch it over to the "Mouse" tab in the configure window. Slide the Horizontal "Cursor Movement" Slider all the way right. Hit okay. It should look like this:
Now you're all set. Whenever you want to play FH2, open two copies of JoytoKey. There should be two little Icons in your task bar at the bottom right of your screen. Right click them and make sure one has "BF2" (or whatever you named your first profile) checked while the other one has "BF2a" (or whatever you named the other profile) checked. Now you can play. When you engage your Hat Switch in-game, JoytoKey will make the computer think that you pressed your "Mouselook" button
and moved the Mouse in the direction you pushed the Hat Switch. Thus "tricking" your computer (and BF2) into letting you use the Mouselook with your Hat Switch. Only downside is that lose control of your plane while looking around, but that happens whether you use JoytoKey or not.