So here's my new effort (again, wishing that I had the odd billion dollars to do this whole business my way
First movie out; Iron Man 2
Main plot is essentially IM and WM up against The Mandarin and his cult/terrorist group. Part of the plot is the failure of Stark Ind. to find alternate revenue (continuing Stark's ending of weapons supply in IM), and attributing to his developing alcoholism.
Back story, Stark is spending millions on another large arc reactor to sell the 'power' to the public. Ending of the movie is basically the reactor test is a success, and we end zooming into the machine until you get to the heart of it. Small rough-shaped piece of metal, that is self-generating electricity (see where I'm going here?). The reactor makes a pulsing sound, fade to back, cue credits.
After credits, fade in looking from above the reactor (again hearing the pulse) and zoom out (POV always down to earth) through the roof (seeing helipad and "Stark Industries" signage on the roof. Continue all the way into space. Eventually a cliff-face enters from foreground, and you see a man, silhouetted by the earth, standing looking at earth. As he's in silhouette, you can't see features, but the helmet and hammer are obvious to fans. And that's the entire involvement of Thor in IM2. No dialogue, nothing more than 10sec in view.
(alt: have him standing on a cliff overlooking the building, i.e. he’s already on earth).
Next movie; Thor
Firstly, I would have the promo posters the same as the last scene of IM2. Links the Thor film to the Marvel franchise, for those non-Thor fans.
Don't know what the current script is about, but my Thor would again be in Viking times. Have him banished to earth by Odin, and somehow (this is why writers get paid) have him have to undertake a journey to north america (this sits nicely with current historical belief that the americas was visited by vikings long before Columbus).
He either finds his hammer along the way or at his destination. He fights an iconic demon (Surtur) who manages, with the first/last (whatever) blow, to shear a piece of Thor's hammer off (you should know where I'm going with this now).
Anyway, he wins (of course) and is teleported back to asgard (maybe even end the film with a similar image from IM2.
Cue to the piece of hammer, time-lapse photography to show the passing of time, (zooming into shard of metal) until you see full screen of shard encased in rock. Zoom out and you see the rock (small brick sized) on a lab table, with a scientist chipping away at the surrounding rock. Zoom out through building and out the roof, and you see it's the same Stark Ind. building as the end of IM2.
There you go. Thor introduced in IM2, without actually affecting the IM2 movie at all really.
Also, this is not the same as FF2’s Silver Surfer, Thor does not lose his powers. It's like your electricity provider will notice that a new neighbourhood is plugged into their network, but it won't suddenly make them powerless.
But they would do something about it, and so will Thor. Actually, if you think about it, maybe it could weaken Thor to the extent that he doesn't overshadow (overpower?) the other Avengers...
Longwinded, but I worked nightshift and had plenty of spare time