Does that mean the rest of the Raza crew have the same personality and ambitions with or without their memories?
Yes, I think that's been an obvious and consistent theme throughout the series. Without their memories, One and Six were still basically decent people, Two was still a natural leader, Three was still a greedy, amoral mercenary, Four was still prideful and ambitious, and Five was still smart, caring, and a survivor. The biggest change was in Two, who tried to become a better person, but we've learned that who Rebecca/Portia became was a response to all the trauma and abuse and loss she suffered, rather than her natural inclination, so in that case it makes sense.
If erased again, why is it guaranteed Three would follow the same pattern?
Three? I think you meant Four. But in fact, both Three and Four have proven to be the ones most willing to embrace who they were before, although Three has found out that he's better off without his painful memories and has proven less willing to betray his comrades than Four/Ryo was.
Besides, we're not talking about "guarantees" and I never said we were. The point is, Three and the Android believe the
risk is not worth taking. The first time Ryo's memory was wiped, he sought to find out about his past, and when he learned he was an exiled monarch, he did everything he could to regain his power and avenge his betrayal. Reset him to the same point and it's reasonable to think he could follow the same pattern. It wouldn't fix the problem, it would just reiterate the problem.
I'm not saying there couldn't be a way to change Ryo's behavior without killing him. I'm just saying I don't think wiping his memory again would be it. We've already seen what happened when his memory was wiped, and it didn't turn out well. There's no sense in thinking that repeating the same action would generate different results. It makes more sense to try something different.
I was wondering if there was a world he could be stranded on. Some backwater class M somewhere. Erase his memory AND strand him. Don't let him access the back up memories or whatever.
If there's no civilization there to support him, that would probably just be a slow death sentence rather than a quick one. And if there is a civilization there, he could gain access to galactic databases and rediscover who he was, just as he did the first time.
Send him to the parallel dimension Portia and Boone are from.
Where there's already another Emperor Ryo Ishida, who would probably kill him rather than tolerate a rival. And if "our" Ryo managed to prevail, he'd just be a cruel tyrant to that universe's people instead of this one's. How is it moral to foist your problems off on somebody else, knowing that they will suffer for it?
Take him back home to stand trial.
Another guaranteed death sentence. You really think the people who overthrew him and tried to assassinate him would be lenient?