This kinda came up to me one day randomly, but I feel like giving it here:
In Simba's Pride, all the Pridelanders knew that the Outlanders had a grudge against Simba, and would not hesitate in terms of murdering others. The Outlanders (specifically Zira) train Kovu to infiltrate the Prielanders and kill Simba from the inside.
So my biggest flaw with the plan is this: The Outlanders settled to being neighbors with the Pridelandrs, thus serving as a constant reminder that they hated each other's guts.
The flaw I see here is this: couldn't the Outlanders leave somewhere else and train Kovu anyways, then he can walk in as a "rogue". He won't have to suffer the immediate hostility just for being an Outsider, and would make his job of killing Simba much easier.
So, what do you guys think?