Depends on what you want to do
Just a few features like mentioned shouldn't be that hard, yes. But if you want to combine the three requirements (hide polls until end, show poll voters, can only vote if posted in topic) it would be a bit more work, especially when you make it an optional checkbox for the poll and if you want to add permissions.
I haven't started, I am currently working on another extension and need to rework some other stuff, but is was th enext on my list.
You can do i if you want though, I don't want to claim any right to do this, feel free
I have lots of other stuff to do
I am not as much confident in extension developing as I want to, but I am working on it. If I can help, I will. Maybe we could do it together, mean: You start and code it, I'll answer questions and help with stuff where you have problems with.