The fact you had to complete a challenge to get them and it was time limited is a major part of the value in them.
Any time something is scarce it adds value, doesn’t matter if we are talking about money, gems, or weapon skins. The scarcity adds to the value of it.
Right now people are creating alts just for the starter gear sets. Why? Because it was datamined they got updated. So now the old sets will no longer be in game. This creates scarcity and that adds value.
Now the opposite is also true. If everyone has something it losses a lot of value. The hearthsteed is a great example. It’s actually an amazing looking mount model. It flys, it glows, and it has a good running animation. But no one uses it because it was given for free and most players have it. Over saturation lowers value.
If the magetower skins in their current form where brought back it would take value from people who earned them. And they where earned. The entire reason most people don’t have them is because even with over gearing the content people could still not defeat the one shot mechanics.
Solution would be a 9.2 new mage tower (not a face roll scaled down but a real new solo challenge) with recolors. Then everyone who claims they where good enough but for some reason where not playing at the time can prove they are good enough to get the new color skin. And those that got the old ones can achieve new colors.