I have read a bit about the upcoming Champion System, but I can't say I have the greatest grasp on the details of it, but my current understanding is leaving me with a bit of a concern, at least about its implementation.
Recently, the immobilization from the 2h charge was nerfed into a snare, upsetting some players. Others offered the idea that immobilization would be rolled into the champion system, and passives may be able to buff a snare into an immobilize.
Also more recently, stealth damage was nerfed, also disappointing many (including myself). I would not be surprised if the champion system also allowed for further buffing of this stat as a response.
There is another thread here which offers a detailed explanation of the champion system and the "pie-slicing" of it, which also worried many tanks in regards to the damage mitigation or armor cap that would be implemented, which would leave them weaker than they are now.
This three proposed changes are worrisome to me because it seems like ZOS is nerfing our current progression and forcing us to earn back what we already have under the guise of horizontal growth via the champion system. If the pattern is to nerf things that already exist to give life to a new system, then all that's happening is we're being forced to grind to reach the states of our builds that we currently have.
Forcing me to work to obtain what I've already worked for is not going to be fun, so I hope this thing doesn't become a pattern. The champion system should allow growth without significant consequences to the growth we've already achieved.