I bought the set just for the fun of it. I play tested and made minor upgrades. I didn't go all out to upgrade it. This is a $10 to $12 budget friendly casual deck.
3/8/20: Added Jiang Yanggu, Wildcrafter to help make mana babies.
Let's state the obvious.
Jiang Yanggu is a bad Planeswalker. 4 Loyalty for 5 CMC.
His +1 is rather meh being it is only until end of turn. But the worst part is a creature must be on the battlefield to even do his +1. Now maybe WOTC figures you're going to use it in conjunction with his -1 but that means if you have no creatures on board when Jiang enters the battlefield you're forced to do his -1.
Moving on to his -1. First off it is utterly useless once Mowu is on the battlefield. And secondly Mowu is Legendary so even if I wanted to upgrade this deck with a Doubling Season to produce multiple tokens the Legendary rule prevents that.
Last we have his -5. And all I have to say about that is it suffers from the same problems his +1 does.
Let's move on to the creatures. Specifically the ones getting cut.
WOTC stated that these decks were created specifically to imbue Magic with Chinese mythology and culture. That might go out the window with upgrades though. Oh well let's get started.
Earthshaking Si gets cut for Grunn, the Lonely King. For the same CMC Grunn makes for a better stompy creature even if you don't use the Kicker mechanic. Furthermore, adding instant and sorcery spells will make Grunn even better when attacking.
Feiyi Snake will slither back into its whole and make room for Elfhame Druid. I figure elves are everywhere and Jiang could use a few mana producers. Plus this elf can help with Kicker spells.
Fire-Omen Crane had potential but we decided since we are going with a Kicker theme we should replace the crane with a dragon. Namely, Verix Bladewing. And with the elimation of land we'll be running three copies.
Leopard-Spotted Jiao is going to get cut for a play set of Lightning Strike.
Reckless Pangolin doesn't make the cut either. He can roll over and make room for three Untamed Kavu. 1 less mana to cast and he has Vigilance and Trample. His Kicker also means he's a potential 5/5.
All other creatures are safe from the chopping block.
Let's move on to instants, sorceries and enchantments.
Breath of Fire simply becomes Shivan Fire. Does the same thing at instant speed but with an added Kicker.
Hardened-Scale Armor will be replaced with Run Amok. We are going for instant speed pump spells rather than Auras.
Cleansing Screech will fall to the chopping block. But its replacement will be Sarkhan's Unsealing. With the new creature additions plus some of the original creatures I expect this card to do well.
In Conclusion.
Well now the deck is designed to be midrange with the option to produce bigger creatures and explosive effects via the Kicker mechanic. Plus adding more pump spells means overwhelming your opponent with scary creatures. Additionally the burn spells help ward off attackers and creatures you can't block. Flyers for example.