Let me elaborate. It would undermine the whole "chance lucky discount" if Riot allowed you to re-shuffle a specific card, so I think there are 2 ways they could go about this:

1. They add a re-shuffle button, one-time use per night market, and it re-shuffles your entire night market, so if you get good skins but not the one you were looking for, you might risk losing that skin for good at the chance of being able to get a better one.
2. They add a re-shuffle button, one-time use per night market, but it only re-shuffles one random skin out of the 5, so you might lose a good skin but you will retain the other four, giving you a chance to get a better skin.

I think this will benefit the people who have terrible night markets, therefore making them want to buy the skins that they will get in the night market by re-shuffling, and rito can make a few more bucks while we also can get the skins we want.