Any engineers out there? Need a simple pallet-elevator

I think you're on the right track with the platform.

I would be tempted to use a block and tackle attached to the pallet and above at the lifting point. Set the winch far enough away so you can use it, to operate the block and tackle.

I would think that would lift engines with ease.

Have you considered the weight you will be putting on the floor overhead? Is the structure going to handle it?