OK - problem one: Here's all the poor, underground living Remans on Romulus' moon, who somehow manage to build this HUGE ship without anyone on Romulus wondering what's that giant thing being built on our backyard. Forget Remans. It's a Romulan ship.
YES, with the Scimitar being the Prototype D class warbird, (Valdore is Clacc C warbird obviously) with the tharalon radiation weapon added at Shinzon's request as he uses the respect he has gained as a militarly leader suting the Dominion war to get him on the development project.
From the very start of Holy Canon, on "Balance of Terror," the Romulans would become aggressive when they thought they had advantage. The magic green pixie dust thingie is their shot to go. So - there goes their test run on Fed outposts. One by one, the Fed loses contact with the outposts, and send out the E to investigate.
Shinzon get to command the prototype warbird and is allowed to test it against the Federation, "Who would not do anything as they have no backbone". Introduces the Romulan belief they were the reason the Dominion War was won, as without their help the Federation was too weak and stupid to win. And the destruction couldn't be blamed on them because the Scimitars new cloak is undetectable.
Outposts there - no people. Thaleron radiation. Another outpost in trouble, so they scoot over in time to see the carnage. Not one ship - a fleet, with one Scimitar as the centerpiece. The E is outgunned 12 ways to sunday, has to withdraw.
Only 1 ship, (as Shinzon's Scimitar is the only one witht a tharlon device).
A spacial anomaly technobabble provides a possible answer to the mass destruction along with the possibility of a Romulan attack for the Ent E crew but they do not believe it, but they are told by Satrfleet Command, (Admiral Janeway and Admiral Nacheqev) not to rock the boat as there has been a political coupe on Romulus and Starfleet wants to be on good terms with the new Preator from the start. The Ent-E is sent to Romulus, so that Picard can open an olive branch to the new Preator.
The scimitar meets they by delcoaking right up against them instead of being that token distance away.
Meetings, that dinner .e.t.c..
Shinzon's hatred for the Federation and love of Romulus is shaped in three ways:
1. We known he is a clone, so the Romulans may have used captured Dominion medical technology to implant loyalty into Picard clone, (like the Founder do to the Jem hadar).
If they didn't Shinzon would have just lived as Picard fully believing in the Federation and exposing his Romulan creators.
2. The opinions of his Tail Shair creators/guardians on Romulus before his sentence to Remus would have shaped his own, (like the opinions of parents shapes their childrens). Which would have included a love for the Romulan Star Empire and hated for the Federation.
3. The knowledge of the Federation doing nothing to help the Remans, (on a basic level).
Shinzons facade anout Reman equality is a cover for using them as a very loyal army, he is a legend to them, their sucessful leader during the Dominon War, their Liberatorm, to them he can do no wrong. This would have shown Shinzon to be amore intelligent, manipulative, cold and calculating villian, another Khan which is partly shown by his use of B4 as a spy.
I would still have Troi refuse to marry Riker, as it would also have led on nicely from their relationship subplot form TNG and Inserection with Riker regaining his manhood and deciding to regrow his beard. Also it would show she actually has some guts, an opinion of her own, (other then who she wants to have sex with every other week) and just to see his face. This would lead to a possible Troi and Shinzon telepahthic relationship subplot that would end with her using the telepathic link to find a target lock with them both admitting they loved each other but Shinzon understood what she had to do, and she understood he had to stop her. That moments pause to think during the battle would have the same effect those quiet moments in trailers have before the fast paced ending with added plot relevant charcter development.
This would give both characters some much needed depth and give us an insight into how telephathic species relationships might work.
I think Worf is on the ENT E after DS9 becuase he asked politleyto be with his old crew again for a while and the Federation wanted to have the only Klingon in Starfleet back on a Starfleet ship to show possible unity afte the Dominion War. The Klingons are Federation members in all but name and officail documents anyway.
I would also have Data thinking for a while before going to die for his friends like Spock did in TWOK. I would still have B4 become Data though, you cannot kill sucha good character off, and Spiner's age can be shown by simply having Data artificaly age his apperance like he does while being a Professor in TNG finale: All Good Things. Allowing that skunk haircut and line from his caretaker in that episode to be used again and a nice link back to that episode, with Picard smiling as it is said as if he remembers hearing it the first time. Creating more continuity.
If anybody
has be killed off it's either Beverly or Riker.
Riker is killed by Shinzons Viceroy by him grabbing Rikers leg and pulling him down with him after the, "Don't worry is dark in hell line".
or
Beverly dies of nautral causes or by a strategic Reman raid to destroy the Enterprises medical facilities.