I know what you're thinking. Jester, why do we need this? We can use Celestial Explore to convert MS to AC already!
While, yes, the rate for that is grueling, but it still often leaves many with hoards of shards leftover that they couldn't get through. Even with higher MS step costs, this will still be a problem, because you can get plenty of MS from just walking around in Celestial Explore.

I propose, like with Arena Tokens in May, they add a direct conversion of Meteorite Shards to AC. It should be less efficient than Celestial Explore, but a way to help users get rid of their excess Shards without having to endlessly click on Celestial Explore. I propose a rate of about 25MS to 1AC, the same as Arena Tokens.
This rate was determined because many of my friends have several thousand Meteorite Shards left, and even just using them will be a hassle. It can also be adjusted if the 25:1 conversion is determined to be too high of a cost, but with the rate of Shards to AC from Celestial Explore already, I wouldn't recommend going lower than 15:1. This is also optional, meaning that users who aren't sitting on thousands of shards by participating in previous years July Events can just use Celestial Explore to convert them instead of using this method.

As a fun little thing, here's the blurb that can be added to the shop menu over the exchange button:
Meteorite... You smell of meteorite. Do you have any? We will take your shards in exchange for Axion Cores. They are... a delicious snack.

As always, let me know if you no support and why, it'll help me better balance my suggestions in the future!