if you want to add reward traits to NPC's then you can use a mod. This is what you do:
1. Go to ModTheSims and download Deaderpool's MC Command Center
2. Once installed and in game, go to a computer in game, bring up mcc control panel and activate debug mode in the options, or might be in MCac cheats; look around to you find it.
3. Once debug mod is activated, you can shift clock on an npc, click on cheatsims, and then click on add trait.
I do this all the time to apply custom hidden traits I've created to npcs
Have fun!