So a crazy theory/fact came up today and I just want to see if there is any validity to it. Was Vader's suit designed to restrict him from using all of his power? It was said that the Emperor knew that Vader would be more powerful than he was so he designed the suit to prevent him from becoming so powerful.

 

In Legends, there were hints that the suit was designed to be easily overwhelmable with Force Lightning. I think this might not be the case in the newcanon though.

 

I think George said once that if Vader had not been burned on Mustafar he would be stronger then Sheev, but because he was he can only be 80% as powerful.

 

He did. The newcanon seems to be moving away from that though - with the Lords of the Sith novel emphasising that Vader's connection to the Force is not weaker, but stronger, after Mustafar.

 

So in theory he can be stronger then Sheev, but because Sheev has force lightning he can never really go up against him one on one.

 

Pretty much. In the Darth Vader: Dark Lord of the Sith comics, literally the first thing Sheev does after that RoTS "Noooooo!" is to zap him with lightning in order to bring it home to him just how outclassed he is.

http://starwars.wikia.com/wiki/Star_Wars:_Darth_Vader:_Dark_Lord_of_the_Sith

 

I also believe the suit was meant to keep him in pain, and to fuel what dark side force ability he had left, as he could never reach his full potential now.
Though the only time I think he relatively feels good is in a bacta tank like in R1 or in a meditation chamber like in ESB.

 

What's also interesting is that his suit was built prior to him getting burned. Sheev knew he was going to end up in it and Im sure he had it so he wouldn't be as strong as him and make him susceptible to lightning and video above is actually pretty interesting.

 

Vader's suit was designed to keep (whatever is left of) him alive, plain and simple. And yes, his potential was affected and limited, despite his connection to the Force, due to the physical condition he's in. More machine than man.

 

My understanding from some of the novels is that Vaders suit was deliberately defective for two reasons -
1 - To punish Vader for his loss to Obi Wan
2 - After his loss, Vader lost much of his Force abilities both due to his injuries and the loss of many of the the MCs that had given him his Force sensitives. Knowing this, Palpatine designed Vaders suit to cause pain and discomfort to fuel Vaders Dark Side rage and abilities.

 

It's always been true that he grew stronger in the Force after Episode III, through continued training in the dark side. The point isn't that he couldn't develop his abilities further, it's that there's now a hard limit on his potential where there wasn't before.

 

Lucas said that in supplemental material - but a case could be made that the newcanon doesn't subscribe to that, and isn't bound by it.

The Legends ROTS novelization, may have been referencing Lucas:

You did it.
You killed her.
You killed her because, finally, when you could have saved her, when you could have gone away with her, when you could have been thinking about her, you were thinking about yourself ...
It is in this blazing moment that you finally understand the trap of the dark side, the final cruelty of the Sith-
Because now your self is all you will ever have.
And you rage and scream and reach through the Force to crush the shadow who has destroyed you, but you are so far less than what you were, you are more than half machine, you are like a painter gone blind, a composer gone deaf, you can remember where the power was but the power that you can touch is only a memory, and so with all your world-destroying fury it is only droids around you that implode, and equipment, and the table on which you were strapped shatters, and in the end, you cannot touch the shadow.
In the end, you do not even want to.
In the end, the shadow is all that you have left.
Because the shadow understands you, the shadow forgives you, the shadow gathers you unto itself-
And in your furnace heart, you burn in your own flame.
This is how it feels to be Anakin Skywalker.
Forever ...

 

I remember reading that the loss of his limbs is the primary way that he was restricted by the suit because he couldn't channel some powers like force lightning (does make me wonder about choke however).

 

But the point is you haven't provided any evidence to indicate that it doesn't feel bound by it. Vader growing stronger after Mustafar doesn't contradict anything.