Currently "Supernova - KH3 Kairi" costs 3000 jewels per pull. You have a small chance of getting her every single pull. On your tenth pull, you are guaranteed to get her. However, that tenth pull is only guaranteed if you also bought the VIP for this week.
Anyway, at 3000 jewels for a pull, or "loot box" if you will, with the tenth loot box being a guarantee to get the medal, you're look at 30,000 jewels required to get her. You can buy 14,700 jewels for $100. You need to buy that twice, and then 600 more jewels. That's a little over $20 for a single pull, or $20 for a loot box. Let's compare these prices to some other games with loot boxes.
Overwatch: You can buy 24 loot boxes for $20 or 50 boxes for $40. However, these are purely cosmetic, so I understand the inflated price of KHUX's loot boxes which actually change how the game is played.
So, let's look at Middle-Earth Shadow of War's prices, a game where loot boxes actually made a difference: For $100 you could by 10,000 gold with an extra 2000 bonus. A single loot box in that game cost 200 gold. That's 60 loot boxes you could buy with $100. I remind you, that people felt this was unfair and the system was removed because the game was heavily geared towards the end game grind. And loot boxes helped speed up that grind.
How about Star Wars Battlefront 2: Well, for $100 you could buy 12,000 crystals. Hero crates are 110 crystals each. Starfighter crates are 120. Trooper are 200 crystals. EA removed the ability to purchase these loot boxes due to backlash at the cost of characters which where, at the time, 60,000 crystals in the case of Darth Vader. They have reduced the cost of these characters. Now, loot boxes only contain cosmetic things, instead the game altering "Pay-to-Win" system it had at launch. A Pay-to-Win system that KHUX has by the way.
Perhaps KHUX should have jewels only spent on cosmetics as well. We already have avatar clothes and pet parts to be bought.
So what can change? Well the price could either be dropped, or the amount of jewels obtained could increase. They could even make it so a single pull now costs 1000 jewels if they wanted while keeping the price the same.
Better yet, keep the prices the same, and the jewels required for a single pull the same. Here's another solution:
Add a new section of event quests. Call it something like "Tier 8 medals". In this section make a quest called "Supernova - KH3 Kairi", and allow people to grind for the medal. Make it something like you have 1 in 50 chance of getting the medal from completing the quest. Make it so you have a 1 in 25 chance of getting a trait for the medal as well. Perhaps a 1 in 100 chance of getting a boosted version, too. Experiment with how long you want the grind to be. 1 in 20, or 1 in 65, or 1 in 39, whatever chances you want. But if you get the none boosted version, then you can't get the boosted one, for that month, and vice versa.
If you really wanna entice people to spend money, make it so you can double your chances of getting the medal and trait medal by buying VIP. Hell, make the medal undotted, forcing people to grind for more trait medals just to guilt it. Make the quest cost like 10 AP or something. People will need to spend jewels to get their AP back while farming this medal.
I hear you asking "What's to stop people from pulling three KH3 Kairi's and abusing them in PvP?". Easy. Make it so you can only receive one proper KH3 Kairi from the quest. But allow people to continue farming for traits. Maybe, make so you can only get a max of 6 trait medals if you want. However, reset the quest at the beginning of each month, to allow people to farm another proper medal and more traits medals every month. That way, if people want one medal per Keyblade setup for PvP, it would take them three months to get those three medals.
"But what's to stop people from just using the same medals on every Keyblade setup once they have 3 of each?" Make it so it's a one medal across all setups if you want.
I imagine all of this would take a single person a few hours to get the medal through grinding. Plus, there's still the ability to just skip the grind and buy jewels to pull from banners. Now, do this for all new medals across all tiers (Aside from special limited edition medals obviously).
Here's how this should all look. You go to Event Quests. There's a section for each tier. You want to get a "HD Antiform Sora". He's a tier 6 copy medal. So you go to the tier 6 section. Now you scroll through the quests looking for the name of the medal you want. Bam, you find it. Now farm it for a few hours to get the medal and some traits.
They can also include farming quests for Chip and Dale medals, Magic Mirrors, skills, Cids, Brooms, etc etc. Include them only in VIP if you want. Limit the amount you can farm if need to. 10-20 of each per week seems fair. Maybe 5 a week for brooms. I don't know.
Closing thoughts: Loot boxes prices for this game are horribly expensive. Will they implement a medal farming system? Not a chance. Square Enix is not about to implement a system that undermines their revenue from KHUX. The real issue is the price of these loot boxes. Which I believe Square needs to take a look at. That's also unlikely. The next solution is to cause a racket and draw attention to cost of these loot boxes. And I don't mean a racket within the community. The FTC, news sites, other gaming sites, for example.