Nope.
Look, the only reason why we keep 3s/4s and champion them is to get LTs and CPs to get 5s.
If 5s were more common, guess what? People would mostly ignore weak covers and build 5s only. Even now 5s with few cards are usually more useful than fully upgraded 4*s.
Power of 5s is fine considering their rarity. Maybe upgrade costs could be raised a bit - 500k is nothing compared to 350K for 4s.
Nerfing any 5☆ is not going to magically change representation or add diversity. Ok OML/Phoenix get nerfed, am I going to switch to my 11 and 10 cover SS and BiB? No I’m going to sitck with my 420 5☆s or drop down to my 12 championed 4☆s. Why? There’s about 800,000 reasons
The enhanced buyback options are going to have a very hard time compensating us for a nerfed 5* anyway.
How could they possibly value a 5* charcter. My OML, for example is 457, so he has 20 covers invested in him (its like he’s the only legend in the deck I draw from). What value would they need to put on a champed 5* to get you to sell it - even if they nerfed it to death?
The ISO components are the easy ones to put a price tag on. Without these items its already close to a non-starter
There is the >550,000 ISO that went into maxing the character. That’s a necessary first element.
There is the 2,000 ISO / cover that is ‘lost opportunity’ because the covers weren’t directly sold. (Setting aside how terrible that sale price is.)
But after this things get way harder. Could they attach an HP value to the sale of a champed 5* that would make you pull the trigger on the sale? I would argue, ‘no,’ because there is virtually no way for HP to be converted into a suitable replacement character.
What about CP? How many CP would they have to offer to get you to pull the trigger and sell a nerfed 5*?
There was the 20-25 CP/cover that you can see in the champed character - but getting that number back just gives you that many new pulls which have their stated 1/7 chance of giving you a new 5*. But you are more likely to just get 4* covers there, and those are hardly a replacement.
Is the only viable alternative for a nerfed 5* to offer “trade in”? Terms like: I want my ISO back, and I want equal number of 5* covers for one or more 5* characters present in the token pack where the nerfed legend is currently available?
For example: maybe I’d consider the trade if I could give back my 20-cover OML for: 1x phoenix green, 3x surfer blue, 1x IM46 blue, 2 of each color of goblin, and 3 of each color of BSSM. But what are the chances of that actually happening? Heck - I might even just take a 4/4/4 OML (no levels) and then 8 covers for other 5s…
But a handful of CP and half a million ISO isn’t gonna get me to click the ‘sell’ button.