It is good to imagine a way to discourage multi-voting. And actually I like your proposal a lot. Anyone who is actually working to play the game will certainly be building strength. It is the most true metric for determining actual activity in this game.
I haven't given any thought, though, to the actual number of 1000. Someone should do the math and determine how long it would take to get that far using standard strength-building techniques. But it feels like a decent ballpark number.
One this if for sure, though, it is TOO EASY to establish a multi voter.