Congrats on coming up with literally the worst possible solution to this problem.
1. Removing the results of legendary combination is almost as bad as a roll back.
2. The week of progress lost is only giving us all the rubbish items from the event, not even any of the currency needed for the contract (which btw people who already got the contract likely didn't farm or used on the pink quest). This means one less week to farm up 50 for most people versus what those people would've been prepared for.
3. If this is an issue of "fairness" the most fair way would have been to just send everyone the contract (the key would've prevented people that already opened the contract from doing so again).
4. The number of people playing your game are dwindling, so your solution is to nyerk off the 300 people that already got it instead of just trying to make everyone happy by giving the contract to those that didn't?