This seems to be a real big issue when looking at it with the current rarity of acquisition of 7 Stars. Essentially people are able to acquire extra 7 Stars for no extra price, is it replicable? Possibly. Will people be using this to break the endgame meta for something like Battlegrounds? Absolutely, if they can do this consistently.
Not sure how realistic it is for Kabam to manually remove the extra champions, I know a lot of people will be up in arms about this, but you have to think about what this will do to the game if it stands unchecked.
As shown happening to Campo;
https://youtu.be/jS_7Q0TYyTs