When you say Alien, I'm thinking Wanamingos.
If that were the case then yes. But aliens as in Mothership Zeta? No.

No they should just remain as an easter egg or a one off side minor event that isn't excessive as MZ.

There was concept art at E3 of an Alien in suit like in fallout 3 next to the crashed recon ship, only difference was the suit was Red with a blue light in centre of chest.

Two alien corpses, an alien weapon, and a trail of incinerated bodies make an unambiguous statement that aliens are real in the Fallout universe.

I personally loathe followers, except as pack mules, and collector items that I keep parked at wherever home is.

Yes, I collect followers, but, only use them to "decorate" my home, like human house pets or something.

Technically they are not "aliens" as in totally alien, they are far away descendents to humans, that is "humans" from the future from a parallel reality.

They have lost their ability to reproduce even technically, so they come here, to their "past" to gain DNA and genetical aid to keep their break-away civilisation from going under.

But yea, I also "predicted" that Bethesda would maybe make this easter egg thing where we help an "alien" and in return we get some tech and maybe a follower.

Having an alien as an easter egg is fine but not as a companion.

It could play into the Institute having some of the most advanced known technology. The government was know to be reverse engineering alien tech, maybe the Institute have a captive alien you might have to free. Perhaps that is how they gained their knowledge regarding advanced synthetic life forms, advanced plasma weapons, and cryogenics. Cryo has not been seen anywhere else in this game universe other than Mothership Zeta, unless I'm forgetting something. So is that just coincidence? Maybe we find out.

Wasn't Skynet's brain in cryo?

Skynet was created from reverse engineered alien technology. So while I may have been wrong about this being the first time we see cryo tech, but in all examples of it, I am pretty sure its all reverse engineering. Perhaps that is why the Commonwealth is where this technology is focused. Because that's where cryo technology and weapons where being created from alien intel. Perhaps the scientist at MIT have been working on it all this time.

I like the plausibility of MIT reverse engineering Alien hardware.
I have always thought, even considering MZ , that aliens do have a place in FO.

I still don't like the Idea of an alien NPC, or a huge quest focused on actual aliens, though- It's too on the nose.
To an extent, aliens existing and providing tech- without being present- is subtle and adds richness to the lore- without kicking you in the balls.