This is the ultimate dream idea for me, Captain Britain is a thoroughly enjoyable character, originally designed as the British equivalent of Captain America. While some have always seen Captain Britain as a bit of a joke, I can assure you, some of us Brits love him. It's super bad ass that we got out own slice of the Marvel pie (he is not the only one), however for me, he is one of the better British characters. My ideal actor to play Brian Braddock, would be Charlie Hunnam, huge fan of his work, can see him being a pretty bad ass Captain Britain.
I'd love to see the "Captain Britain and MI-13" arc by Paul Cornell from 2008 adapted to the big screen. I read it last Summer and it revived my love of Braddock, I'd like to think a lot of British fans of the MCU and the books would like to see this arc included in the future of the franchise.
(There is talk Cap B, being part of X-Men universe so owned by Fox, would love confirmation if anybody knows either way, thanks in advance).
Captain America 4
I'd like to see the "Madbomb" arc from King Jack Kirby himself adapted for Bucky, I know it is Cap and Falcon however pretty simple to tweak it a bit to have Bucky and Falcon teaming up to save America. While the stories started off brilliant towards the end they fell off a bit, but there is so much to take from that arc I think would be perfect on the big screen.
Guardians Of The Galaxy 3
I will be honest I have read VERY little Guardians, before the film was even announced I wasn't even aware of them. Since the film though I have read some stuff, personal favourite is "Cosmic Avengers" by Bendis, McNiven and Pichelli. It's a very fun arc which I could see James Gunn doing perfectly if he were to make the third instalment, which should NOT be called "vol 3".
With this character being so young, I decided to choose a Thor arc I particularity enjoyed I not so long ago read the Surtur Saga and couldn't put it down. I'd be a happy camper if we ever got to see that arc adapted to the big screen even with my complaints of Loki in recent times, I would put that all aside to see this wonderful arc by Walt Simonson which is possibly in my top 10 arcs of all time.
Spider-Man & Daredevil
Let's be honest ANY arc in which Spidey & Daredevil team up to take down Kingpin, this is all I have wanted in the comic world.
Iron Man (barely) 4
As for the story, really hard to say, I do not want a reusing of a previous Iron Man arc from the books (not that I am familiar with any late teen Stark arcs?). I'd rather see a completely original story used in this.
Avengers 4 (2 parts)
Avengers consist of Cap, Thor, Scarlet Witch, Skye, Cap Britain, Daredevil, Spidey and new Iron Man.
X-Men consist of Cyclops, Beast, Jean Grey, Wolverine, Mystique, Rogue and Gambit.
That seems like a LOT of characters I know, but this stroy-arc needs a good amount of members as the book cover shows. It's a fun run, if you haven't read it I recommend it. This would be the perfect way of bringing the entire Marvel back under one banner. May be a strange way to start off a world after such a story, but I can see it bringing in a lot of fans into the MCU that aren't already here (if there is many left), it may come across as a similar approach to Captain America Civil War in the way it's clashing the heroes. That being said I can see this being Civil War and that bit more on the big screen, in the book form Civil War is better I just see A vs X making a brilliant film maybe even better than Civil War translation to the big screen.