Here’s what I’m coming up with for Mr. Fantastic. Don’t know about the numbers, honestly, and he’s far from a “top-tier” character, but what I was really going for was something fun and different from anything we have in game based on his funky power set (I wish they tried something more creative for “stretch” powers when they made Kamala Khan).
All Tied Up 
(14 AP)
Mr. Fantastic stretches forward and wraps himself around a target enemy, effectively removing them from the fight. Stuns the targeted enemy for 1 turn and creates a 1 turn Blue Countdown tile that activates every turn, stunning the enemy originally targeted by this special ability. If Mr. Fantastic is dealt 500 or more damage from a single attack, if he would use one of his special abilities, or if the target character or Mr. Fantastic are the only remaining members of their team, the Countdown tile is immediately destroyed.
Level 2: Countdown tile deals initial target 70 damage each time it activates.
Level 3: Countdown tile deals initial target 210 damage each time it activates.
Level 4: When the Countdown tile is destroyed due to Mr. Fantastic taking damage, the initial target of the ability is dealt damage equal to 30% of the damage done to Mr. Fantastic.
Level 5: When the Countdown tile is destroyed due to Mr. Fantastic taking damage, the initial target of the ability is dealt damage equal to 65% of the damage done to Mr. Fantastic.
Elastic Genius 
(10 AP)
Choose a row. Mr. Fantastic stretches out and punches the enemy, dealing 300 damage. He then swaps the chosen row randomly with any other row on the board.
Level 2: Deals 410 damage.
Level 3: Choose two rows. The chosen rows are switched.
Level 4: Deals 650 damage.
Level 5: Mr. Fantastic can use this ability and does not destroy the Countdown tile placed by All Tied Up
Fantastic Friend 
(Passive)
When Mr. Fantastic’s entire team would be damaged by an enemy’s special ability, he stretches himself out to provide complete cover. Mr. Fantastic takes 200% of any damage done from any enemy’s special ability that targets your entire team, but his allies do not receive damage.
Level 2: Mr. Fantastic takes 180% of the special ability’s damage and reflects 10% of the damage to the enemy character that activated the power.
Level 3: Mr. Fantastic takes 150% of the ability damage and reflects 25% of the damage to the enemy character that activated the power.
Level 4: Mr. Fantastic takes 130% of the ability damage and reflects 35% of the damage to the enemy character that activates the power.
Level 5: Mr. Fantastic takes 110% of the ability damage and reflects 15% of the ability damage to the entire enemy team.
The blue is a bit of a different take on the stun locking offered by characters like Daredevil. It does tie up your Mr. Fantastic (but that’s not too great a loss … by design!), but it basically ensures that you don’t need to keep track of a particularly troublesome character for most of the match. Makes the game 2 vs. 2 for pretty much however long you want it to be. At the same time, the AI won’t be able to use it very effectively (breaking it off early by firing another of Mr. Fantastic’s abilities, or simply by you making Mr. Fantastic the target of your next reasonably powerful hit), so it really shouldn’t take away the fun for the player when Reed is on the other side.
The black ability isn’t entirely my idea. I think I actually first saw something similar proposed by another user in the Quicksilver character discussion when he was still officially “Unknown 3-star”. Initially I was worried that the Black ability would be too similar to Quicksilver’s with better damage, but if we’re being honest, Quicksilver’s is still better. Swapping specific tiles is always useful for setting up matches and such, but swapping rows is really only consistently useful for moving special tiles into or out of harm’s way in the presence of specific board damage ala She-Hulk and Rocket & Groot. Plus, Quicksilver has a built-in, if not entirely reliable, method of reducing his ability cost.
The Fantastic Four is a family and they pretty much take turns sacrificing themselves for the sake of the others. It’s what they do. Anyways, this seemed a perfect way to fill a hole in defense abilities. Colossus and Deadpool are all too happy to throw themselves into harm’s way, but being consistently the size of an average person means you can only cover so much space with your body.
Honestly though, I feel like the basic concept of all of these abilities work and mostly different from anything we really have in game. As a plus, I think the abilities mostly work with the ideal 
color combo.
