Storage No Poof

This mod preserves the items inside block containers from removed mods, and turns the removed block into a special block which, when broken will drop all items the container used to have. Alternatively if the container had many items and you do not want to potentially cause server lag, you can extract the items out of the block until it's empty, in which case it will automatically self-destruct.

Right now only mods which stored their items in a top-level Items tag can have their data preserved (this tag is used by vanilla containers too). In the future, options for modpacks to define rules to keep items from specific tags and inventories will be added.