Headcanon/theory time:
What if Ninety-Nine was meant to be a member of Clone Force 99??
The Kaminoans definitely played around with the accelerated aging rate of the clones, seeing as Omega was created before the Bad Batch, likely just after or around the time generation 1 and Boba were created for her to be old enough to remember the Bad Batch’s creation. This would also mean that the Bad Batch were likely created along with generation 2 for them to be mature enough for combat. Additionally, if Emerie is a Jango clone and Omega’s sister, the Kaminoans clearly gave her a dose of whatever accelerated her aging.
We know from TCW episode 03:01 “Clone Cadets” that training squads consisted of five troopers, but the Bad Batch only originally had four. There’s no real reason the Kaminoans would have deviated from Clone Force 99 having five members… unless something went wrong.
The Bad Batch still would have been functional as a squad of four if their training had been adapted to that of the commandos. I’m hesitant to say they were originally intended to train and operate as commandos, because their designations are CT-9901, 9902, 9903, and 9904 respectively, not CCs.
So, if there were supposed to be five Bad Batchers, who would CT-9905 have been?
My theory is that Ninety-Nine was originally created as part of the Bad Batch and was designated 9905, but something went wrong with the “desirable” mutation in his DNA that caused him to age far too rapidly. Upon seeing this, the Kaminoans removed him from the Bad Batch, but kept him around to see the results of their twisted experimentation. That means the rest of Clone Force 99 could still have been aware he existed, and maybe Ninety-Nine even looked out for them as he continued to rapidly age. It would also add to his desire to be a soldier like the rest of his brothers, and his strong sense of camaraderie. That would account for the Bad Batch knowing of his sacrifice when the droids attacked Kamino, and likely formulating Plan 99 in his honor.
Finally, it would make the situation even more poetic that Echo, who knew and befriended Ninety-Nine, would come to be the fifth member of the Bad Batch.
