If we can build automated Turret, we should be able to build simplified robot like protectron.
I think it will also be fun if we can customize Codsworth a bit.. haha. At least color.
I think it would be a good idea, plus I wanted to build those sentry robots. And if we can't build them maybe we could buy them.
Also if we were to build the robots I wouldn't mind building them and having them in charge of stores. that way they are 24 hour stores like the one in diamond city. I tried assigning codsworth to the store but he wouldn't go over there. He even stopped moving in general. so getting the robots would be a great idea, in my opinion anyways.
If you are on PC, a mod on NexusMods.com exists which allows your character to build robots for settlement defense. The mod is named http://www.nexusmods.com/fallout4/mods/5787/? by TheTalkieToaster.
I can vouch for this mod 100% though there are a couple of caveats.
1. Your character needs to have the Robotics perk level 3.
2. Once you place a robot it cannot be moved or otherwise the robot will power-down and I've found no way to get it going again.
Hope this helps.
Mods are limited because of no GECK, once its out I see three options to get an robot, hack an robot and reprogram it, shoot it up and then repair it some materials and science, build it your self far more materials and high science.
You can assign it like an settler with limits, an handy or gutsy can do anything the other only guard.
You could also have them as an follower and hopefully deploy them at locations, next to boss in the overused MM radiant quest locations would be nice
Deploy is leave follower and have follower holding position.
Moding robots, mostly upgrading weapons and armor, an sentry bot for settlement defense is better off with two galting lasers and no missile launcher or explode at death.