That’s right but it could experimented into an Event (Quests) and against Titan. It could be used for a new class of heroes.
However, the idea could be experimented and slowly introduced not necessarily took as a “whole major change” into the game logic.
After all, how many heroes like Christmas Heroes have special abilities that trick the common plain rules of the game? All of them.
Even in the case the editor decide to introduce this feature for the whole game, the introduction could be done graduatelly. At the beginning only 4, 5* heroes at the maximum ascention and progressively to the others until it would be a general rule.
Is the idea interesting. Does the idea brings value for the editor and players? Yes and yes. Then a way to introduce it without messing the whole game is always possible. Progressive introduction would be a nice way to do it.
Another way to introduce the feature? Those pay the VIP access would have this feature on their multi-stars 3, 4 e 5* heroes. In such a case the feature could be fixed to the heroes (useful to increase their value on the market among players the day it might be in place) or fixed to the gamer/pay per month (which is more meaningful because as long as the player is a VIP does not should worry about how the heroes came from).
Finally, the feature could be sold as VIP+ package. They could reduce the fee of traditional VIP membership (in my country is €5.49, about $5+VAT) by 20-25% in order to enlarge the user’s paying base and then offer the VIP+ for a surcharge.
In my opinion the could have a good value return if the lower the VIP to $4 net (in my country it would be €4+VAT which is €4.89 – between €4.49 and €4.99) and raise the VIP+ to $6 net (in my country would be €6+VAT – between €6.49 and €6.99). I suggest the combination of €4.49 and €6.49 which the halved sum will be €5.49 spread over an enlarged paying base.
The VIP and VIP+ could increase the user base about 20% bringing for the editor a 10% more revenue with a higher degree of renewal in monthly option especially for those bought VIP+.
After two months of VIP, at the third renew the editor could give a VIP+ for try-before buy. I have the sensation that many would stick with VIP+ after they have tried it once for free.