Currently there are no way for a storage node to decrease their size. Say if a node has 1TB of used storage, and they want to go to 500GB of storage there is no good way of doing that.
My solution is to allow the 1TB node to go down to 500GB by simply prevent this node from getting any download data, until they are under their desire size. So the node can only upload files and delete files. I believe this is a better solution than a partial graceful exit. It will not be as fast as a partial graceful exit, but it will be able to drop down to the desired size naturally.
This can be an flag or argument as part of a docker command, or simply reducing the size of "STORAGE" environment variable and the node knows to not download.