David Tennant is a very talented actor, in whatever capacity he is needed for whether it being a ing role or a lead role.

He is Scottish by the way, I had never heard just how thick his Scottish accent was until watching him speak with his natural accent.

He is good at imitating other accents like some American accents and some British accents.

There was an episode of Doctor Who where a sentence gave him trouble, you could clearly hear his thick Scottish accent. Other than that one sentence you wouldn’t have known.

I have seen him act in Doctor Who, where he was a bit quirky, but also one that you didn’t want to make him angry, where he does the following in a 2 part story "Human Nature" and "The Family of Blood"

“Father of Mine: The Doctor locks him in a ** unbreakable chain** and throws him to the bottom of the ocean.Mother of Mine: She's trapped in a permanent state of immobility, resembling a scarecrow.Daughter of Mine: The Doctor traps her inside a mirror.Son of Mine: He's frozen in time and left to serve as a sentinel. “

I have seen him playing Casanova, and even in bad guy roles where I greatly despised the character in which he played. 

I think he could play a believable Mr. Fantastic Reed Richards. They need to give him a chance like they gave to Robert Downey Jr. for Iron Man and Benedict Cumberbatch with Doctor Strange (who they waited for him to play the character when his schedule finally opened up due to scheduling conflicts).

He is of their caliber of an actor in my opinion. 

Not bad for ones that make a living playing make believe for others to enjoy.

If they were to give him the chance to play his dream role Reed Richards, I am sure everyone would notice how good an actor is when they are playing a role that they would enjoy playing.

But the writing has to be good with a good storyline and good actors playing the other characters.

This is my opinion keep in mind.

The more I think about it, there is two personalities within Anakin/Vader’s mind.

both personalities coming from the now fractured original personality, splitting or about the time of Anakin’s mothers death.

Where it was the Vader personality that took over slaughtering the whole tribe, women and children too.

Over time the Vader personality would gradually take over Anakin, through manipulation by senator Sheev Palpatine Darth Sidious/The Emperor, and his use of the dark side.

It was just Disney being lazy and mes another successful franchise after they acquired the rights to them.

Honestly it would have better if they stuck with George Lucas‘s plans and ideas that he gave them for three films that he had written decades ago, when he sold Star Wars to them, because he didn’t think he could be able to make them due to his age.