Generate a class system, and try to create a balance. Don't let this game turn into a Pay To Win game. Only have level ups, money and only money so you can buy clothes and customize your character (NO ARMOR OR STAT THINGS.) Stuff like stronger weapons and armor ruin the game for newer players. Level ups just unlock new clothing and colors for your guns. Also add more guns with more classes.
For people who want the 4th achievement:
1) Play a pretty easy game with a small town
2) Reclaim everything in the town
3) Train people with level 10 Leadership, Offense, Building, Scavenging
4) Give them all weapons and send them to a new city
5) Set the dificulty to seriously hard and small town
6) It will be much easier to do with all the skilled people you have.
You pick locks by pressing W to push it up (hold it to make it go farther) When you hear a click that is the sweet spot. Wait for it to come down and do it again, then press d at the click. Thumbs Up so all can see!