That could collide with other global hotkeys you might have in your system
This.
What about removing the Soldat tray icon feature instead.
That f9 thingy is really not needed.
There are enough ways to go back to your desktop. ( windows key , alt-tab, ... )
And as an added bonus, it would save a function key. Which could be used to get rid of the problem with the alt-f3 shortcut. You know when you want to check you fps and you end up pressing alt-f4 by mistake.