I'm not really here to say that the current method of obtaining Mega Rings is bad. The only thing I don't like is how the Mega Pokemon spawn in the wild which isn't very lore friendly. So I thought I'd just make a suggestion, take it or leave it in the end its the Devs decision whether they want it or not so here goes!
Reason for Suggesting
The only reason I'm suggesting this is due to the fact that I'd personally rather disable the wild megas and have it so once the player reaches a certain point in their adventure (I run an adventure server) they can mega evolve. Basically there would be a command "/givemegaring" or something along those lines which would allow server owners to have things like the final gym or the end of the elite four grant mega rings for end game usage. The command would simply just give them the ability to equip the ring so that they can use it with the mega stones. I just thought I'd request this so that servers could utilize other methods to give mega evolution and so I could balance out my server without removing mega evolution. As always nice job on Pixelmon and see you around o/