Well, I used the complete item editor tool to change the name of the Gold Teeth to Mega Ring, then added a Mega Stone item the way you would add any item really, making it a hold item with no effect. Made it so an NPC gave me the mega stone to test it out, this is the result I got

So what you're saying is I can just rename the Gold Teeth to Mega Ring/Charm/BraceletAnklet and it will work?

I messaged you a few days ago about the Keystone. Turns out all you have to do is change the name in an Item editor to Mega ___ or Keystone or something and it changed it on the message. The same goes for Megastones, just add them as items (I added just a simple Mega Stone item and only put one into the game). Have someone give you the Key Stone item before you get the megastone and it seems like its all okay!

Actually, the keystone check is broken...

Hey dude, love the mega base it'll come in handy when making a rom hack, I do have a question however. Is there a way to change the "keystone" Item from Gold Teeth to anything else at all?