Yes... speed is the tradeoff. You double the pulling power but halve the speed. This is because you now must take in twice as much cable to go the same distance.

If you've watched Dirty Jobs on the Discovery Channel, there was an episode where during a military training exercise he recovered a stuck humvee with nothing more than an elaborate block and tackle and people power (no winches). Sure it took forever to rig and moving was slow going, but its possible.

In theory, your idea may work, but in practice, its a really bad idea. in addition, the 2000-3000lbs atv winchs are always short drum... meaning, you got half as much cable as a normal winch but you're using twice as much for the same distance (w/ your block and tackle). You won't have any effect winching range with such a setup. What good is a 5' pull to an object only 20' in front of you?

-Rob