The clear solution is as follows; Add a Scottish-inspired race to the Horde. They'll never be able to do anything Scot-free again.
On a more serious note: Even if she is forced to abandon vengeance against Sylvanas that does not mean she has to abandon it against the ones that executed Sylvanas' moronic vision.
And also Tyrande is just that: Tyrande. Even in accepting her rule dissent is certainly possible.
Also Greymane may have a word to say about the ultimate fate of the Forsaken and the banshee before the end.