This idea is for an items with small inventories, that you put tools inside of, and which can be used as (better versions of) the tools inside.
For example, a connected blocks container, that you put a pickaxe into, and when you use the container on a block, it acts as if you'd used veinminer or ore excavator with the pickaxe on the block.
Also, an All In One Tool container, which you can put one of each type of tool, and with the container, you can attack, mine, chop, shovel, shear, fish, and ignite nether portals. The container itself acts like some sort of AIOT, but only one internal tool is used (and loses durability).
Also, a tool enchantment container, which holds one tool, and when you use that container, it acts as if you were using a version of the tool which had whatever enchantments were on the container instead of the enchantments it actually has. So you can enchant a container with silk touch, and put your fortune pickaxe inside, and when you use the container, it acts as if you were using a silk touch pickaxe.
Also, the ability to put a few stacks of empty buckets inside the connected blocks container, look at some water or lava, hold down the right button for several seconds, and then either the buckets are full or the liquid is gone. Obviously, the container needs to force full buckets to stack inside it, but that's not a hard trick.
An omni wrench container, which you can any whitelisted wrench, hammer, or similar (wand of the forest), and using the container on a block selects whichever tool inside came from the same mod as the block.
A tool stacking container. Put several identical tools inside of this, and they stack in it's inventory. If you have 3 pickaxes in it, and you use them on a block, and you would have lost 1 durability, then there is a 1/3 chance that all of the pickaxes lose durability, and a 2/3 chance that none of them lose durability. Especially useful if you want to use golden tools.