Cave update mole: neutral but is territorial of its burrow only if you steal something from their burrow in their line of sight, live in burrows in the mountains or in caves will attack if you steal from their burrows they collect items such as ores, rare cave treasures usually shiny objects if they are found with a partical effect white=common, gold=rare, light blue=exotic, means they have an item you can feed them to get said item but it's random the can also drop used pickaxes that can help you get out of a tricky situation if you are trapped in a mine...
They will steal anything that you drop that is either an ore, pickaxe or something shiny and if you don't catch them fast enough they will take your item and put it in the burrow..
there very territorial about their burrows and if catch you stealing from their burrows they'll all rally up and try to attack you..
Baby moles can be raised and can be taught to dig cracked stone to find treasures and Random loot..
moles can also sniff and find ore clusters, the best tamed pet to bring mining, the only way to tame one is to get a baby and feed it mole milk which is produced by adult moles also can be used in a potion to find ores and burrows. (The potion Acts by making a particle trail to the closest or you're near to)
To get mole milk you can find it in their burrows but you'll have to wait for them not be around to take it or it can be found in a trade for feeding an adult mole...
Moles eat worms (can be found as a bi-product from digging large amounts of dirt) worms can also be used as bait to attract bigger fish..
along with the update there could be a new type of villager called the archaeologist that will collect cave treasures found in caves. you can sell them all the treasures you find from moles or just by mining in general..
fishing villagers will be updated to have worms as bait as a purchase..
redstone golem from Minecraft dungeons put into ravines and giant caverns and especially in ruins the update will also add random abandon ruins in random cave systems that will have small chests with different golems protecting them..
some ruins will have a lapis golems ,some will have an emerald golem when killing the golem of whatever ore you will drop large amounts of that ore they're composed of also depending on the golem type will depend the rarity of items found in the chest at the back of the room.. so if the chest is being guarded by a diamond golem, you can get some pretty rare stuff in the chest..
Ruins (typically made of stone bricks looks like a rooms from the strong hold) but failed attempts or old buildings left behind, it has a random ore type golem at the center guarding the chest..
Along with this update should be added that the following creatures should have bioluminescence inside caves: cave spiders and slimes killing these mobs can drop bioglow which can be used to make glowing dyes and natural glowing colored blocks in all the dye colors, also dyed armor that can be used to make a glow sticks effect on armor also to make glow sticks that can be thrown and last for 1 hour of light so miners who aren't planning to make that mine permanent can save the resources..
random glowing blocks found in caves to add atmospheric light, fog found in caves to add mystery and a spooky feel when searching around in big mining shafts..
what ever biome you are in the cave walls will represent it, example if mining in a jungle biome you will find moss on the stone walls and find lots of plant life underground..
with this cave update will be a new type of glowing mushroom that provides the player with haste but the mushrooms are very rare to find and can only be found in bioluminescent areas...
New procedurally generated caves would have to be added to support all of this also procedurally generated burrows for the moles and a new building for the archaeologist villager I feel like this would make a great cave update and it is exactly what Minecraft is missing to make cave adventures exciting