It was (and is) fantasy.
There will not be the next Emperor? Why not? Of course there will be. Natiosn need leaders. Leuluch is dead. Someone has to take the throne. And somebody after that. Etc, etc..
Zero as a symbol will stop tyranny? LOL. when has zeros existence stopped anyone before? His actiosn did, not his existence. Not to mention it won't last. Suzaku is no Leuloch and can't be the proper next Zero. And when he dies, what then?
'Next Emperor' in the way you put it. Besides, after the whole incident with Lelouch I doubt imperialism will last much longer.
Zero is a symbol because he remains. Or don't you see him in the epilogue making negotiations. He will exist to preserve the message of justice and equality for all. He killed the 'demon' Lelouch, he put an end to his tyranny. It doesn't matter WHO lies behind the mask, but what the mask represents. That's why the world can find relative peace under the efforts of Zero (Suzaku.)
There is a slight possibility (under theories of course) that Suzaku is the same as C2/CC now. I don't know the details, but the explanation is reasonable enough. Basically it's the same way C2/CC got her power.
But let's say that he isn't immortal and does die. It's the basics of legacy. Martin Luther King was shot dead, but it doesn't mean his legacy didn't live on. He remained a symbol for the Black population to fight for equal rights and others took his place too. Zero, alive or dead, literally saved the world from a tyrant. This was Lelouch's plan, to make himself the common goal that people will strive to go against.
The only reason CG makes it seem like a happily ever after is because the nature of the ending. But Kallen herself said 'there's still a lot more to do' or something along those lines. There will be political fallout, there will be war and there will be other conflicts.
If there ever were an R3, it'd be interesting on how it'd develop Suzaku's character and show just what the consequences of his plan are. How it wouldn't work perfectly and how there'd be a lot of struggle to keep things going smoothly.
And lol no. A 'world without lies' is simply terrible. F*ck I'd hate that. The Emperor was a nutbag to begin with. If there was ever a huge flaw in CGR2 is to try and add misplaced 'depth' to the character.
Just imagine it all. Yes, fundamentally it'd make us 'better' but is that really all that good? Might as well make us all hardcore Christians too...
As for Reinhard...
There will always be a hierarchy. I'd rather have him at the top than a-holes like Job. But he remains grey all the same. The cost of conquest and war is a terrible thing and better leave the alliance as it was....
Which he did, he left the alliance government working on its own until they f*cked it up by messing with Yang Wenli and he had to step in. GOD even AFTER Yang Wenli escaped from custody and set up a resistance Reinhard and his bros still didn't see the need to put the blame 100% on him. They fought him out of necessity, not out of vengeance.
Still, I completely, 100% disagree with you that he's a d*** or any where near it. F*ck, if it wasn't for him the war wouldn't have ended. The Imperials would carry on and the alliance would never have stopped. One side had to win in the end.