[Ryoko was her greatest creation for a very good reason. Besides, the gems were useless to her. They just wouldn't work, so she built something it would work for. It was brilliant solution.]

If it were Ryoko, I would understand why age would be impossible to pinpoint, but since it's not, there should be nothing stopping you.

[Yes, she needed to focus on something else, something non emotional. Science fit her needs rather well. Especially now.]

If you remember, I arrived at the tail end of the doppelganger fiasco so I don't know much about them. However, If they were created, I would consider the possibility of clones raised in a laboratory. It would be nothing to grow the body and then kill it without the clone ever being alive to begin with.