Forgive me if someones already come up with this type of story!
If like me you were a tad dissappointed with SUPERMAN RETURNS and the direction they have taken the franchise in (i.e seemingly backing themselves into a creative corner with the super-kid and all) and the fact they decided to cut the whole return to krypton scene (which they shot AND finished!) read on:
My SUPERMAN RETURNS sequal synopsis:
Firstly,the title would be just "THE MAN OF STEEL",this is also in tune with the Batman Begins sequal being called The Dark Knight.
The way I think they should handle the movie,that would please fans the most is that Braniac could have been the one to send signals of Krypton to Earth (seeing as how they never used the fact that LEx was originally supposed to have fabricated the whole thing) and Superman could have brought the core of Brainiac back with him from Krypton without realizing.
Its a great way to use the Return to Krypton sequence in the sequel
Braniac could surface from the buried ship (at the Kent farm),and go on a mission to destroy and assimilate superman in his all powerful body of last Kryptonian,then learning about Jason,he could focus on him instead-as a much easier/weaker target.
Richard could die protecting Jason from Braniac (nothing against the character,it would just fit,both dramatically and to progress the story),superman could then decide to use the fortress chamber to de-power Jason,turning him fully human to protect him and give him a more normal life (no more SUPERKID) .
Superman then needs to kick the hell out of Braniac in a super-fight scene (come on,who doesnt wanna see supes fight "neo and agent smith in matrix revolutions" style...without the kung-fu obviously)
Well,thats my ideas anyway...