I know it probably won't happen, but I'd like to see them either pass over Lex Luthor entirely or have him be a secondary character in the next film. I'd love to see Brainiac and Darkseid introduced, although I can see why they might steer away from the later with Marvel using his equivalent character in their current cinematic story arc.
They need to have a character with some firepower though. Another Luthor and kryptonite movie is exactly what doesn't need to be done again.
		
		
	 
I think I would like to see Luthor but in a different way - as the mastermind behind something and make it a character that can be in a movie or two as a larger arc.  The whole ending a super villan in one movie thing isn't exactly in keeping with the comics and I think forces them to sometimes make bad decisions to keep getting new bad guys.  So do something where Lex is the boss and Superman has to stop whatever he is doing but doesn't catch Lex at the end - almost Empire Strikes Back like.
And I agree with the poster that said Lex needs to be a homerun - and they need him to be much much darker than the others.  Spacey was ok and HAckman nailed it perfectly, but there was too much comedy in both.  They need to make him sinister and evil without humor.