Oh god, this would be awful.
What if you lose the dupe? What if you want to dupe it more than once?
Jesus, that would be terrible.
Then simply don't use it?
Just because it is made doesn't mean you have to use it.
Are you mentally changelled (I'm actually curious, not trying to be insulting if you are)? Honesty, it's one extra click. If that's too complex for you I wonder how you're even capable of typing.
The same can be said about the duplicator, you can just make a macro, just because its one extra click to do without it doesn't mean you have to do without it.
Its a suggestion, and a pretty good and useful one.
Also, didn't the Swiss Army Gun have a feature like this?
I can't remember if it only moved one brick, or a whole stack.
-snip-
If it were to be made, it should be with a limit of about 150, of course a preference though.
And if it hits the limit, just simply stop the whole process, and give the player a time-out of 5 seconds to prevent flooding.