What can I do with settlers?

So when it came to settlements I tended to have one large central town (in my case the drive-in) where I'd have well developed farms and vendors etc. My outlying towns would get less attention. So on a recent visit to one of them I noticed I had a population of almost 20 and almost everyone was just standing around with nothing to do. Now I know settlers can

1. farm
2. be vendors
3. guard duty
4. pack mule for supply lines

Is there anything else i can do with them?