Expansion of Treasure Chest subroutine

I thought about using 6 bytes if I was not going to be successful in eliminating the need for the event byte. But thanks to you, I found a way to do it!

Regarding chest randomization, I have three options in mind:

• Shuffling every chest among themselves. (Kind of boring)
  
• Randomizing chest contents but offering items or gold from the same tier as the original item, as you mentioned. (Mirage Vest in the Cave to the Sealed Gate, perhaps?)
  
• Anything goes on! (My personal favorite)
  

But doing so will open the possibility to have better equipment in an early chest, hence the need to be able to open every chest.

I also want to randomize secret item locations, e.g. the clock, the armor, the fireplace and wherever Arvis checks when he takes the Slave Crown in his house could potentially hold an item. On top of that, since the game currently has a little more than 270 chests, there is still place for at least 200 other secret items. I want to see how many more of these could be added before it starts to feel ridiculous.