First on the chopping block was the ridiculous Weapons & Ammo quick select thing, I find that menu particularly hateful with a mouse.
Although I still don't really grasp how the actionscript in the swf is interfacing with the game ifself, I managed to cobble together a perfectly functional and fast radial menu for the weapons in the quick use slots.
Instead of having the ammo and weapons appear at opposite ends of the screen, the ammo appears right in the centre with the 4 weapon quick use slots around the outside of the ammo, so you don't have to go across the whole screen to get from the weapons to the ammo.
The menu also now works on mouse over instead of clicking on anything, so you just move the mouse roughly in the direction of the weapon (they have great big hit boxes) then back to the middle on the ammo you'd like to select and let go of the modifier. I'm actually surprised at how well it works at this stage.
Obligatory screenshot: http://imgur.com/a/VIIMR
It's still pretty ugly since I pretty much just butchered the existing two menus to throw it together, but I'll tidy it up a bit tomorrow while I work on a few other things I'd like to try add to it and I'll upload the hud.swf and .fla files for other people to use them in their own mods if they'd like, there's not really much point in bundling it into a mod on its own.
I'll probably shorten the opening and closing animations quite a bit just so it's a little quicker to use but I'd like to figure out how to get the game to pause for a menu, like when you open the inventory, but I've a funny feeling that's not actually part of the menu file and the game itself does that before opening the menu.
If I can find a way getting all the weapons on there, that'll be sorted too, I just haven't come across the code for that yet.
There should also be a way of checking if the user is using a gamepad or a keyboard & mouse in actionscript, once I find that I'll be able to have both menus in the same file at the minute it's just the mouse friendly one.