I used Looksmenu mod to make a playable alien, going to make it an artificial life form with player.setrace synth in console and AI brain chip integration with player.modav intelligence 19 because 30 is the highest attribute point total an NPC has in vanilla and with 10 intelligence plus bobblehead it is 11 with +19 enhancement = 30
And will start a custom settlement with alien settlers at a landed UFO.
UFO Location mod: https://www.nexusmods.com/fallout4/mods/20138
To recruit alien settlers: https://www.nexusmods.com/fallout4/mods/47065
I've tested both and they work perfectly, the UFO is an ideal player home and bunker.
To add stuff to that location as a settlement. https://www.nexusmods.com/fallout4/mods/12511
And to scrap things in custom settlements to build with and to make room for building things. https://www.nexusmods.com/fallout4/mods/66811
To run the settlement without human farmers to produce food copy and paste setav 331 3 into Notepad, save it as FOOD.TXT and place that TXT file in the game's installation folder. Then click on an alien settler in console and type in BAT FOOD then press ENTER. Repeat with every alien settler. When viewed in workshop mode again they will be foraging for food to feed themselves.
To not get nagged about mods and console commands not allowing achievements use Place in Red Reborn achievements with mods enabler. https://www.nexusmods.com/fallout4/mods/14601
The custom settlement has its markers in very dumb locations that are not vanilla and place them all in one spot at the center of the settlement which is not realistic. Use this mod to move the attack markers further away and spread out so enemies spawn beyond your view not materializing right in front of you.
https://www.nexusmods.com/fallout4/mods/38738
Enemy attackers are there to try to steal from your workshop, move it with Place in Red Reborn to a building's roof where only you as a player character can access it directly by moving a ladder, build a ladder to move it around. That way all they get is aliens.
To play as the leader of the alien settlers with a collective mind and receive experience points from settlement attackers they kill. https://www.nexusmods.com/fallout4/mods/44520
https://www.nexusmods.com/fallout4/mods/54471
That way all you have to do is watch and observe like a real alien leader would with 30 intelligence XP gains. Place all AID items in the workshop, that's what attracts settlement attackers most in the game mechanics. And keep your defenses no higher than 20 to entice attacks and be able to have 20 settlers which is vanilla max with 10 charisma. 2 heavy machine gun turrets and two spotlights, for example. On the roof with workshop inaccessible to NPCs and accessible to you by moving a ladder. There will be cake, the cake is a lie.
An additional touch to make it more sci-fi is to place a Star Trek red alert intruder detector on top of the settlement center marker revealed by the view settlement markers mod. https://www.nexusmods.com/fallout4/mods/54471
As a secondary alert system that allows you to see where hostiles are a mile away marking them on your compass there is a Patrol Eyebot mod that patrol the outer edges of your settlement at the in-game mod store. It can be stored to remove it and placed again. Red Alert tells you it's time to defend or attack, patrol eyebot alerts you to their presence. Aliens will seek out and destroy automatically during alerts.