There are plenty of models and recolors for cosmetic items in the game that just go unused by everyone because they either only last 3 days or are of green quality, both of which are not much use, stat-wise.
My suggestion consists of recycling all those items so that they can become relevant like the current orange/gold quality ones, through one way or another, with the objective of introducing more variety into the game, as well as giving the player that choice without having to fall behind in stats.
Before we get into how this could be implemented, I've compiled a list of these items (might not be 100% complete or updated), as well as screenshot previews for some of them. There are quite a lot, so if you have decent screenshots of any of these items that I haven't gotten a hold of yet, please post them below so I can add them. For the majority, these consist of mounts and face items, but there are also a few of the others.
Now, X-Legends could just do this the easy way, make gold versions of all these mounts, orange versions of all the other cosmetics, throw them in lucky packs for the Item Mall or in the Paragon Table and call it a day. Maybe even put them in the Loyalty Shop - all of which would be just as fine, too.
However, at the same time, we could also include them in some events, perhaps even as drops in certain dungeons. Maybe have a new type of Mount Upgrade Stone that works with the old versions of these items. Though a lot of them are very hard to get now, so we would need to make them more accessable again.
If you have any interesting ideas, feel free to leave them here.