After Sailor Saturn had awaken in Sailor MoonS, she was aware of how strong her powers were. Being the Sailor Scout of Death, Destruction, and Rebirth, Sailor Saturn was well aware of the fact that she was the most powerful of Sailor Scouts. Saturn had mention to Sailor Moon that she could have help her more if she was able to keep the Holy Grail. Sailor Saturn needed Sailor Moon's help so she can be reborn. Sailor Moon had the Silver Imperium Crystal. Saturn was aware of the powers of the Silver Imperium Crystal. Sailor Moon was able to recieved help from the other Sailor Scouts. Therefore allowing Sailor Moon to help Saturn in the fight against Pharaoh 90.
Sailor Saturn was one of the two persons who had the powers to stop Queen Metaria, and her allies. Queen Serenity was the second person had the powers to stop Queen Metaria and her allies. We know how Queen Serenity was able to stop Queen Metaria and her allies briefly during the Battle of the Moon Kingdom. Queen Serenity had to used the Silver Imperium Crystal at the cost of her own life. It is likely one of the powers of Sailor Saturn had was the ability to protect Queen Serenity from the dangerous effects of the Silver Imperium Crystal whenever she needs to used it.
If Sailor Saturn is included in the new Sailor Moon anime seires, we will notice that Sailor Saturn will play a critical part at the end of the series. I will rather see Sailor Saturn to contimue to be a sleeper in the new series. Naoko is one of the few people who knows what are the plans for the new series. If Naoko decides to include Sailor Saturn, Sailor Saturn will likely be Serena's twelve-year-old sister. After Serena beocmes Sailor Moon, she becomes aware that her sister Hotaru is a sleeper. Yet, Serens is only aware of the fact that Hotaru is a sleeper.
I agree with everything except for Hotaru becoming Usagi's younger sister...that doesn't make any sense and I can almost guarantee you that it's not going to happen. All of the Sailor Soldiers' names have to do with their respective celestial body, and having "Tsukino Hotaru" as Sailor Saturn would mess up that pattern. And that's not even the best reason I can give as to why it won't work; others include having to re-write the entire S/Infinity story arc and change Hotaru's connection to the Death Busters. It would just be a mess.
Personally, I really think everybody needs to stop exalting Saturn's role so much and just treat her as a normal Sailor like any other. It's clear that Hotaru wants and likes to be a Sailor Soldier because it gives her something she's wanted for so long: acceptance. Her power shouldn't be a detriment.
It's only her civilian self during S who'd wanna be accepted, as she was feared by her classmates back then due to her strange powers, caused by her being possessed by Mistress 9. I don't think Saturn the Senshi would really care about whether she'd be accepted or not, as she's only concerned w/ her mission, which's the very purpose of her existence/awakening/appearing, & her fellow Senshi would (at least ultimately) also understand that.
I imagine she can't play "big and bad" all the time in uniform since none of the other Sailors do (not even the Outers).
In S, Sailor Saturn is depicted as a separate entity from Tomoe Hotaru...so, yes, she can play "big and bad," unlike the other Outers. By Sailor Stars, based on the few times we see her as Saturn, I think they were made one and the same like the other Senshi.