My guesses for some gameplay alterations, minor or major; whatever.
1 - Inventory Upgrades System
Nintendo will hopefully make it so Korok Seeds are still a collectible, but not required for inventory upgrades.
Instead, I hope that they would make it so that Inventory Upgrades are done through a merchant character like Beedle and that you spend Rupees to upgrade your inventory for Melee Weapons, Bows, and Shields
After all, how redundant did Rupees become in BotW by the time you were half-way done with the game?
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2 - Tingle Returns
We now have islands in the sky.
And Beedle is our wandering trader that is found at stables.
But what about that goofy odd-ball of a man in his mid-thirties who thinks he is a fairy, makes maps & charts, and conveniently has a balloon contraption he flies around with?
Why not bring Tingle back and have him be an explorer of the sky islands and a merchant in the skies so when Link is adventuring way up high and possibly running low on resources, we don't have to go
all
the
way
down
to
the
surface
in order to buy supplies from Beedle or a village?
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3 - DLC Returns Old Content
Do we already have a save file of Breath of the Wild?
Do we already have the DLC content of Breath of the Wild?
Why not have that DLC content carry over into Tears of the Kingdom?
After all, Nintendo claims TotK was supposed to be a lot of DLC content that was instead made into its own sequel.
So why not have the DLC contents of the previous game carry over?
The outfits and the end rewards of the Champion's Ballad of course.
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4 - Amiibo Support Items, Old & New Stuff
So.
The Amiibo items that you obtain from BotW's catalog of weapons, bows, and armors should make a return.
But what about some new stuff as well?
Why not have us scan Toon Link's Amiibo and get the Conductor outfit, Four Sword, Phantom Sword, Lokomo Sword, Hero's Shield, Mirror Shield, Spirit Tracks' default Shield, and The Minish Cap?
Why not have us scan Twilight Princess Link's Amiibo and get the Ordon Sword, Ordon Shield, Wooden Sword, Wooden Shield, Ordonian Attire, Zora Armor, Magic Armor, Zelda's Rapier, The Ball-&-Chain, and The Hawkeye Mask?
Why not have us scan the 8-Bit Link Amiibo and get to unlock the Koholint Sword, White Sword, Magic Sword, Bunny Link Outfit, and the Pegasus Boots?
Why not have us scan Ocarina of Time Link's Amiibo to unlock the Megaton Hammer, Kokiri Sword, Razor Sword, Gilded Sword, Great Fairy Sword, Hero's Shield, Deku Mask, Goron Mask, Zora Mask, Stone Mask, Couple's Mask, Hero's Shade Armor, Hero's Shade Shield, and Hero's Shade Sword?
Why not have us scan Skyward Sword Link's Amiibo to unlock the Skyloftian Attire, Braced Wooden Shield, Fortified Iron Shield, Goddess Shield, Ghiriahim's Rapier, Ghirahim's Claymore, Ghirahim's Demon Sword, Groose's Glutes, Groose's Dukes, & Groose's Mousse?
There are just so many options to choose from to be frank.
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5 - Blacksmithing
Gathering resources and materials was an integral part of Breath of the Wild.
Why not expand upon it?
Weapons are breakable.
BUT
You can find molds out in the wilds that will allow Link to spend rupees and resources to craft weapons, shields, and bows of his own liking with the bonus of the perks such as Durability Up?
And if you have a weapon you really like, you can save it by going to a blacksmith to have it repaired, for a small fee of resources and rupees depending on how extensive the damage is?
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6 - The Return Of The Picori/Minish Race
In early builds of Breath of the Wild, there were going to be Picori people in tiny villages here and there that Link could encounter.
For the most part, they seemed to use recycled models from the Hylians of Skyward Sword in the images that were unveiled from early builds.
Reintroducing these little people in some pockets of Hyrule could be an interesting touch. You're out exploring and suddenly, while climbing a rock face POOF! You stumbled upon a small cave inlet with a small Picori village! And they are willing to trade things and possibly have a quest!
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7 - Bringing In Co-op
Imagine it.
You want to play Tears of the Kingdom but you also have a sibling who also wants to play or you have a buddy or GF/BF who also wants to enjoy the adventure with you?
Well, pick up the second controller and suddenly Player 2 is playing as none other than Rinkuru/Linkle !
The backstory of this iteration of Linkle could easily be that she is Link's great-great-great-great grand niece, a descendant of Link's sister or brother he had before the Calamity struck.
Linkle's family told stories about their couragous relative and Linkle is inspired to travel the world and make a name for herself.
And so, when she and Link encounter one another; she decides to help him in his endeavours so that they both can be heroes.
All the while not knowing that the person she fights monsters alongside is the very same man her parents and grandparents told her about in stories from her childhood.
Linkle will have more feminine style clothes than Link, will be allowed into Gerudo Town regardless of what attire she is wearing, and will use Crossbows instead of Bows as her ranged weapon.
A Non-canon addition to the game's story but a canon addition to the world lore as she may very well be travelling Hyrule in the aim of making a name for herself instead of being a cucco farm girl.
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8 - The Return of Items
I hope that some items from the Zelda franchise make a return as an optional non-breakable item that Link can equip once he obtains them by cycling through the same list of powers his arm-bangle-thing grants him.
So not only will Link have the powers of the Sheikah Slate and the arm-bangle-thing, but lets say you want to climb in the rain.
How best to do this?
Well, if you find the fabled Double Clawshots, you can grapple onto the mountainside and climb upwards with ease!
Seek to disarm your enemy opponents? The Whip from Skyward Sword makes its return and allows Link to steal spoils and have a chance to disarm the enemy with a quick flick!
Want to scout ahead? Make use of the beedle to fly about and see what might be spawning down the road when you reach render distance or to fly up high to places you cannot reach yet to see if there is anything good to find there.
Want to walk on water? Well, find the fabled Hover Boots and you can walk across small gaps and walk on water for a short period of time before they give out under your weight.
Same with waking under water. Equip the Zora Hood and the Iron Boots and you can scour the seafloor and lake beds for sunken goodies.
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9 - Fire Emblem Crossover
Have an optional cross-promotional questline in which Link gets to meet some of the famous characters of the Fire Emblem series.
Similar to how Xenoblade had an easter-egg crossover in BotW, Tears of the Kingdom should do one for Fire Emblem.
Simply put, a spell in Fire Emblem had caused a rift in space and time, scattering famous characters such as Roy and Marth and Ike across Hyrule. Complete small quests for them and you can obtain replications of their weapons and outfits as rewards!
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10 - LET US PET THE DOGS
11 - AND ADD CATS THAT WE CAN PET TOO!
12 - LET US ADOPT CATS AND DOGS TO HAVE AT OUR HOME IN HATENO !!
13 - LET US HAVE A QUEST TO TAME A BEAR, A DEER, A BOAR, A SKELETON HORSE, HEBRA RHINO, AND THE LORD OF THE MOUNTAIN TO HAVE AS AWESOME MOUNTS TO CHARGE INTO BATTLE !!!!!
14 - LET US BUY PROPERTY AND RECREATE A SETTLEMENT FROM SOME OF THE RUINS SO THAT WE CAN MAKE MORE TERRY-TOWNS !!!!
Some of these are obviously wishful thinking.