More/different recolors of the rift outfits
Currently, the rifts only feature blue (deep rift) recolors of the cosmetics found inside a rift. They are pretty, but they're getting old. Rift after rift after rift it's all just blue...
Don't get me wrong, I think that it's great that you started adding recolors like this. It enrichens the rift. However, you could go some much further. The easiest thing is simply changing the deep rift color with every rift. Make 1 rift have red recolors! Some other green, etc. There's soon gonna be an overabundance of blue recolors. -_-
People love variety. Look at Fortnite for example:
This picture shows the 3 types of recolors in the current battle pass. First you get the red recolors (like the 4th character in the picture). 5 characters get such red recolors. Then you get the rainbow recolors (like the 2nd and the 5th character shown here). And then you get the tiger recolors (like the 1st and the 3rd character shown here).
So each of the 5 characters gets all 3 recolors within the same battle pass. (not counting different clothes styles and optional headgear/mask that they get as well). Also, these recolors are animated .
I know, Fortnite probably has a much bigger budget than DBD. However, look at this. You could take DBD so much further with the rift skins. Just having blue recolors in every. single. rift. is gonna get veeeery boring. You need to open up to various styles and colors, if you want us (players) to have much more fun.
If that makes DBD rift go from level 85 to 100 or 150, so be it. People are willing to use money to buy the missing tier levels when the season/rift is approaching its end. I do it with Fortnite. I would also do it with DBD.
I hope you consider this win(money)-win(variety/fun/goal) scenario. :)

Comments
I forgot to mention that the characters in Fortnite also get additional outfit recolors (not shown here) when you do special (weekly) quests. People (including me) love to grind for these. Opening up DBD for this would be huge, in my opinion.