Hoestly, I personally see it as a choice between Aria T'loak and the Shadow Broker...who do I want to help keep/gain power. Sloane will be happy to have and rule Kadara whIle Reyes will have his hands everywhere and be just as ruthless as Sloane...just more hidden and prettier up. To those that point out he did not grab a "tbrone" like Sloane...the most powerful people in politics are often those BEHIND the throne and hidden. I would rather have the devil that is out in the open, and known than the one hiding behind a mask weaving intricate web...
This is again, just my opinion and we will have to see how bioware plays it.
As far as Ryder taking over goes, don't see the issue...Outcasts are leaderless, Collective is leaderless, Ryder could bring in initiative to calm things with help from Angara. Some of both may fight, but you would have cut the heart and soul out of both....and no reason you would have to have been an oppressor, much the way you could take over in Elendan....take over administration, and show fairness, people would respond.