I think a good sized wooden box is about the right idea and put a spring loaded flip door at the top and ramp in it so that the boxes can slide down without being all bashed up. Then put one way spikes on the ramp all pointed the same way... the packages can slide down but if an idiot actually climbed in to steal a package, they’d never be able to get back out. Or better yet, have it slide down a ramp into a locked basement area... assuming the house has a basement.
Or just have a door with a coded lock... the delivery person has to call when arriving and you can give the code over the phone and even watch as the package is placed inside and then the door locked up. Then change the code for the next delivery. Would delivery people do that in the interest of
A coal shute.