Well, the advantage would be dead mollies after the ammonia goes up and then they rot and get the cycle started.
The raw shrimp will do the same as the fish, whether it's poop or decaying shrimp, the end result will be the same.
If you have live rock in there, wait before adding anything to see how much ammonia will come from the die-off on the rock. If the ammonia doesn't amount to anything(less than 1ppm), add the raw shrimp and let it decay until the cycle completes. Just test everyday for ammonia and make sure it doesn't go over 4-5ppm, if that happens you will have so much ammonia it will kill the bacteria as well.
A couple months patience is better than buying fish left and right for nothing. Don't take the first sentence as a smart mouthed comment, I was just saying what will more than likely happen, at the very least the mollies would have ammonia burns and not live very long.