I noticed that skyblock has a new feature on survival, (not sure about eco) that if you complete the /challenges, you can claim your own player head as a reward. However if you have completed all of the challenges (not including the newest 7) you cannot claim your player head.
My suggestion is to add a button in /challenges to claim the player head so that players who have completed the challenges prior to the update can still claim their heads, while people who have already completed it cannot claim it again.
(Sorry in advanced if there's a format I needed to follow, I couldn't find it. long time since I posted on the forums.)

 

If they could just add in an extra challenge so it would trigger the head pop up that would work for the player that already completed them. However they would also have to add a way so people whom have completed the challenges after the update don't get two heads.