I wrote a very similar idea in a thread a while back…
Each year at the game’s anniversary they make some special offer that is similar to this. We got one guaranteed mythic from 40 gems (20 paid gems) in the recent anniversary, which was a great idea. Maybe next year we could have an “anniversary shop” be added for two weeks with a collection of some of the best legendaries and we all get given a special ticket to buy the one we want most. Perhaps we get this special ticket from a guaranteed mythic 10-pack (like the one from last year). Hence, we buy the 10-pack with 40 (20 paid) gems to get 9 randoms, 1 random mythic and then get to also select a legendary of our choice.
This was the thread: How cool would be a monster exchange
If I remember correctly, I later wanted to make some slight alterations to this idea but it looks like I didn’t bother to go back and change what I wrote. No idea what they were now. It’s definitely a bit generous but I like the general concept.