Random fighters creation is a feature of UMS 2. Once you are in the fighter explorer, you can just click on the “Create Random” button at the bottom the window. It will create a random fighter for you, so you just need to save it before using it in the sim.
You can also define some parameters before creating them. If you right click over the “Create Random” button you can select the weightclass and the fighter stats cap in the popup menu.
The ability menu will set the cap for the stats this way: Cans (Max 10 in any stat), Average (Max 14 in any stat), Prospect (Max 16 in any stat) and Elite (Max 20 in any stat). The editor tends to create fighters with good stats within the ability so if you set it to create average Elite fighters you will see some 19 and 20 stats most probably.