sure
On one of my forums, I would only want to enable this feature in 1 or 2 threads. In all other polls on the whole site I don't mind how many posts they have.
So for example, if we wanted to enable the post restriction on a poll in this thread, we would input the thread id. -> 284897
So having a box where you can input thread id's separated by commas, would be cool

(Unless you can think of a simpler way to do it)
Hope that is clearer ^^