Yes this would be a good swing emulation ... am I'm not saying it's a bad idea, however it's also not necessary. You can set the pulley low(waist) as well and it would still be equally as effective. Still using the same muscles. Same thing with the medicine ball, no need holding it up by your shoulders.I would set the pulley at the height of your hands at launch position
I like the medicine ball more personally.. so versatile and dynamic. Overhead slams, Diagonal overhead slams, side throws etc.. excellent workout.. and the kids find it lots of fun as well