Here is a pair of modified default.lua files for the F-16C viper that includes the scripts needed to map the ejection seat arming handle to keyboard or joystick. Three new commands will be found under the "Systems" category. Two for direct mapping and the other for a toggle. There are no other changes present in these otherwise stock files.
The commands can be located under the line -- Ejection Seat Lever if you want to copy them into another modified default.lua.
Ejection Safety Lever, LOCKED
Ejection Safety Lever, ARMED
Ejection Safety Lever, ARMED/LOCKED
The files are placed in the following path: