Creamy Sheev could easily pretend to be a Jedi. He pretended to be a harmless politician in EP1.
Remember that Sith and Jedi are distinguished by 2 things: fashion sense and Force Aura.
Kaminoans wouldn't sense the second, and the first he could just use makeup, they are aliens. I doubt Kamino had advanced humanology lessons 101: Is this old human just old or a Sith? They don't even see in the same spectrum so maybe even the Sith eyes wouldn't be noticed.
It would have been a funny scene to show him cosplay.
Now, with that out of the way... I'm going to be honest here, I wasn't sure how I was going to respond to you, sir, because frankly you got yourself a bit of a reputation in this thread. I might not post a lot but I do lurk a shitload. I've seen the arguments in this thread that you've been a part of. There are times when you're annoying and times when you're not. With that said, you do have a bad tendency to white knight for Lucas. Pointlessly, if I may add. I'm not going to deny there's people out there that tear the man down but goddamn he's a grown man and it's OK to criticize him. This is something to be criticized. Do I need to point out K.I.S.S.?
Keep It Simple, Stupid.
He has a simple explanation in place. Sidious pretended to be a Jedi to order the army. That's not complicated. The Kaminoans were adamant? Who fucking cares. You're saying they can't be fooled by someone? Let's talk reality for a moment. How many people get tricked by cunts pretending to be police? And those cunts don't have the resources like someone like Sidious would. You really think Sidious couldn't pull off pretending to be a Jedi with his level of access and power? The resources at his disposal? C'mon, man. Don't be silly.
Realistically, if it was Sidious who ordered the army, then the Kaminoans would start saying something along the lines of "hey, the Jedi who ordered the army looks a lot like the Chancellor" and the Jedi would not trust the Clone Army, since the Chancellor ordered the army behind their back while pretending to be a Jedi, which would signal to the Jedi that A) they cannot trust the Clone Army, and B) they cannot trust the Chancellor. Ergo, they stop using the clones and start raising armies of their own, drafting local soldiers from Republic worlds and the like. Which makes Order 66 and the rise of the Empire impossible, since from day 1, the Jedi would never trust the clones, and they would be even more suspicious of the Chancellor, who not only went behind their back to order the Clone Army, but he deceived people into thinking he was a Jedi, too. They would build up their own military and power structure, hampering any plans by the Chancellor to turn the Republic into an Empire.
Meanwhile, if it was a Jedi who ordered the Clone Army, a Jedi who actually sat on the Council, then it's easier for the Jedi to swallow the idea that the Clone Army is trustworthy; it was ordered by one of their own, a Council master no less, so even though he went behind their backs to order the Clone Army, he was one of them, he was a Jedi, so the rest of the Jedi go along with it and it's easier to fool them into trusting the Clone Army, which makes Order 66 possible, which makes the Rise of the Empire possible.
If anything, AGAIN, this was a good retcon on Lucas' part, paying attention to detail. It certainly is preferable to Disney and the Sequel Trilogy going for the "keep it simple, stupid" approach and not giving a good explanation as to why things happen in the Sequels. How did the Empire return in TFA even though the New Republic ruled the galaxy? Keep it simple, stupid, just don't give a shit, enjoy the lasers and the explosions, and eat your goddamn popcorn. How are the Resistance in TLJ suddenly become so short-handed even though they had the support of the New Republic? Keep it simple, stupid, just accept the fact that they're the scrappy underdog and the hidden Empire now has even bigger Star Destroyers and Super Star Destroyers than they did when they controlled the galaxy. How did Palpatine return? Keep it simple, stupid, just accept that he's an evil wizard with magic powers, and that revival is one of them.
Literally, the "keep it simple, stupid" approach is why the Sequel Trilogy is a forgettable wreck, especially TFA, which is just a carbon copy of ANH with not a single original bone in its body. They kept it simple, kept the worldbuilding and the politics to a minimum, and at most RLM and the normies liked it, but RLM aren't Star Wars fans, they're Trek fans who have always hated Star Wars, and the normies aren't fans either; they're called normies because they're only there for simple entertainment. Which explains why now, even the Disney Star Wars faithful no longer care about the Sequels and instead care more about things like Andor or the Filoniverse, since simple films don't do anything that remarkable and are forgettable slop. They left the "simple" movies to rot in the desert while they moved on.
Hell, if you applied the "keep it simple, stupid" idea to things like the Original Trilogy Star Wars or Lord of the Rings, nobody would remember them. They would just be standard fairy tales of the good guy killing the shit out of the bad guy and moving on. No complex lore about the One Ring, no "I am your father", just simple-ass good vs. evil that has been seen and played out over a thousand times. Those two stories would just be forgettable fairy tales rather than iconic franchises people keep ripping off or emulating.
Meanwhile, for all its flaws, people keep meme-ing the shit out of AOTC and the other Prequel films, people keep coming back to them, people consumed media that revolved around it in droves, even as they castigated them. Meaning that these films were still iconic enough and they left enough of an impact that people remember them even after they came out over a decade ago. Can you say the same thing about the Sequels?
Again, I'd rather have an autistic idiot like Lucas running Star Wars than the "keep it simple, stupid" people at Disney who didn't give a shit about details. The former made Star Wars iconic and memorable, the latter made Star Wars into forgettable slop, to the point where even now, barely anyone gives a shit about the Skeleton Crew show coming out. Back then, when we had an autist running Star Wars who said "nuts to that" to the "keep it simple, stupid" approach, even the fucking tie-in novels, comics, and video games were selling like hotcakes. Never mind the actual films which still made the fans happy. The attention to detail that the Star Wars universe had under Lucas made it a lived-in world that had its own culture, its own feel, which made it more unforgettable, as games, comics, and novels set in that universe had that unique appeal that you could rarely find anywhere else.
If you keep it simple, nobody gives a fuck after the adrenaline dies down. Who here remembers Arnold Schwarzenegger's Commando? Good film, but at the end of the day, it's just a simple "muscle man guns down 1000 brown people with a machine gun" movie, and you'd struggle to find someone on the street or the net who even remembers the fucking thing without them having seen the Nostalgia Critic review of the film which came out over a decade ago. Even the GOOD works that go with the "keep it simple, stupid" approach have been lost and forgotten to time.