Wills and testaments and suicide notes off the top of my head.
How many wills and testaments include the words "I wish"? Also, if it's something grandiose and vague like "I wish the world was different", then what would happen? (Plus, what are the chances that someone with the words "I wish" in whatever their writings were happened to be buried in that particular graveyard?)
I imagine that would happen, my head cannon is that the cemetery has no limits
psst it's "headcanon"
Yeaaaahhhh this makes it crazy overpowered and a lot harder to write up convincingly.
The SCP would interpret the intended meaning through unknown means
This doesn't tell me anything about what actually happens, though.
That one is kinda tricky but I think it could be explained through an urban legend existing about the graveyard. From there the foundation notices things are fishy and moves in.
Why would an urban legend just happen to exist regarding the graveyard that just happens to be anomalous? Seems like a cop-out explanation.
I think an idea like this could really work.
Keep in mind that as the author, you know the entire story, but the Foundation needs to have discovered what it knows about the SCP through observation and experimentation. How would someone with no prior knowledge whatsoever of the object, using only experimentation and observation, come to all the conclusions you've outlined above? You're definitely going to be fighting an uphill battle with suspension of disbelief with this idea.