My mod addresses this by implementing the following
-A structure at settlements to make settlers mercs
-An additional source of income at your settlement
-Radiant quest at your settlements.
You construct a mercenary post at any settlement. It jas a few chairs, a desk and looks like a wanted poster wirh poorly scrawled pictures of mutants and raiders etc. The mercenary post serves as place for settlers to issue warrants for things minutemen wouldnt really get involved with such as collectinf bounties on people. Some of the jobs advertised can be quite unscrupulous.
You can assign up to 3 settlers. They will sit at the desk, lean against the board etc looking idle. Speaking to them opens up a trade menu where you can buy 3 types of items.
1) Their contract, they will follow you like a companion and behave like one but they can die permanently.
2) bounty / assassination missions. Small fee to take (Commission) from the menu and has caps reward. Bigger priced missions reward more caps but harder.
3) Stealing / acquiring illicit goods contract. Steal X item fron X noc etc etc.
Mercenary posts can be legitimately there to provide services of escort for people in need or they can be full on thief and assassin guilds if you wish. Good companions may disapprove of buying these contracts. Best of all they behave just like stalls giving you income. Requires same as other stalls which is caps collector perk and local leader.
It will be nice to have companions which can spend time with but they can die!
BUT WAIT THERES MORE!!
You can rename the settler to anything you want including any settler not even assigned.
Purchasing a mercenary makes them permanent companions until they die or are unassigned. (Because u general of minutemen so they wont keep charging you unlike other people)