A note on rebelling: People tend to have the most difficulty rebelling immediately after being taken over, since it comes as a surprise and they do not understand what is happening. The longer they spend with the parasite, the longer their brain has to work around it. After a certain point, however, their rebellious nature starts to drop again, as the parasite adapts to its host and the brain begins to forget what it was like without the parasite. The host is perfectly capable of active rebellion at this point, they simply don't WANT to anymore most of the time. They've grown tired by the fight and just give in.
However, with a rebellious of 5, they will always have some self control, and the initial takeover is not nearly as strong.
You have two options - You can either choose to remove rebellious directly, OR you can work just one end of this curve.
Buying a point in something like "Adaptive Control" would hasten and strengthen the tail end of this process - the longer you spend in a host, the better you get, and the more secure your hold gets.
You can also work the other end, and make it so your initial control is stronger, but you don't adapt as well over time - the longer a host is infected, the more they remember of who they once were. You develop into more of a symbiotic relationship than something like outright dominance over the host.
Both of these would probe much cheaper the removing rebellious completely.
For an example of the second, see most modern day vampire movies.