Fantastic Four

Short Answer: Ditch the origin; connect to MCU through the Skrulls

There have been four Fantastic Four movies. People are familiar with the one (2005) that got a sequel (2007), and then the reboot (2015). And then there was one from 1994 that was only made so that the studio could hang onto the rights to the characters.

All did poorly.

But now, the characters are owned by Disney, and so they are going to get yet another chance (which is several more chances than DC has given poor old Green Lantern).

How are they going to do this right?

First, ditch the origin story. It's simple enough-- scientists go to a space station, get douses in cosmic rays, receive superpowers. We have told it twice in movie before. This time, tell it wordlessly during the opening credits as a montage and get to the story already.

(Cracked.com has a great article on origin stories so baked into the culture they need not be told again on film but can be assumed known by the audience. The F4 origin was not on their list. So I say, OK-- tell it again, but in five minutes. Don't make it the plot of the movie.)

Also, in these other cases, the F4 have fought Dr. Doom. He's a good baddie, since he uses both super-science and magic, and runs a small European country called Latveria (somewhere in the neighborhood of Latvia, we assume?). But, we have seen him already.

Instead, we should use another foe, the Skrulls. These shape-shifting aliens were introduced in the Captain Marvel movie and Spider-Man: Far from Home, but referred to in Guardians of the Galaxy,  and were also seen in the WandaVision show. So, we MCUers know who they are.

But... in Captain Marvel's origin movie [spoiler!] they get retconned into being the victims of the Kree, and are now sympathetic. Then again, they are seen as a threat still because they are shape-shifters and can become anyone.

So, now we have our in for the F4. They get their powers and master them. Now, they are chilling in The Baxter Building-- their high-tech HQ-- when the get a visit from Nick Fury. He knows Reed "Mr. Fantastic" Richards is a science brain on par with Tony "Iron Man" Stark, Bruce "Hulk" Banner, and Hank "Ant-Man" Pym. 

But those brains are busy. So he asks Richards to develop a way to scan for Skrull DNA-- from a distance-- to make sure they are humans and not aliens in disguise-- "Just to keep tabs on them." Naturally, Richards is appalled at the idea of spying on people. A debate takes place among the F4 as to whether to comply.

Meanwhile, a Skrull learns of their powers, traces its source, and exposes himself to the cosmic rays (not that hard, since as an alien, he has a spaceship). He becomes Super-Skrull-- I promise I did not invent this character! Look him up-- who can use all of the F4 powers at once.

So... yeah, he becomes the bad guy the F4 have to defeat. He does a bad thing in a way that frames the F4, ("Who else could have done all this particular damage?"). Being a genius, Richards figures out that it was a rogue Skrull. 

Of course, to find him-- since, in addition to their powers, he has retained the basic Skrull power of shape-shifting-- they kinda have to invent the Skrull Detector that Fury wanted to begin with.

At first, they fight Super-Skrull (again, not making him up) with their own matching powers. But then they figure out that they have to counter with different powers. Does he shoot a Human Torch flame? Invisible Girl wraps it in a force-bubble and snuffs it. Does he throw a Thing-style clobberin' punch? Mr. Fantastic bounces it right back at himself.

Teamwork also figures in. His Mr. Fantastic stretchiness is undone by The Human Torch's flame, which makes him brittle enough for The Thing to Punch. And his invisibility? Again, the flame makes him glow hot enough to be seen, and if The Thing can see it, he can hit it. It's important to have these to learn to work together, as they are famously always on each other's nerves.

So, yes-- they subdue the Super Skrull and also make it known that they are innocent but that of course not all Skrulls are bad and to be feared. To drive the point home, Richards publicly demolishes the Skrull Detector and deletes the blueprints for it.

I kinda hate to bring in The Four Elements, since that trope has been done in every movie from the Frozen sequel to, well, The Fifth Element and of course the Avatar: The Last Airbender show. But it has never been really acknowledged that the F4 are what D&D players would call Elementals. The Thing is Earth and Human Torch is Fire-- those two are easy. Invisible Girl represents Air-- and so that leaves Water for Mr. Fantastic, who while not wet is basically a liquid. 

Richards is a man of science, and the Four Elements are, at best, pre-science thinking. But even Richards can see that these were early attempts to codify what we would today call The Four States of Matter: Solid (Earth), Liquid (Water), Gas (Air), and either Energy or Plasma (Fire). So he would say that the alchemists were trying to have these things balance-- so while it's wrong from scientific standpoint, it's still a useful metaphor from a literary point of view.

In the post-credits scenes, we learn that Fury has already copied the blueprints of the Skrull Detector machine, but of course does not tell Richards he has done so. 

Or, maybe, that Dr. Doom has? Also? I mean, once the F4 are in play, we have to have Doom show up at some point.