I know a p. much perfect way to have trinkets and accessories work:
If you have the trinket in your hotbar,they give effects.
No need for like 7 useless new armor slots coughaethermodcough, just have them being in your hotbar be enough.
There should be no craftable accessories whatsoever,they're all obtained from dungeons etc,usually broken(repairable by enchanting for 10 or so levels)and give rather mild effects(no anti-grav super jump invulnerability superspeed imgoddamninvincible shit coughaethermodcough).
For example,a Bracelet of Life,boosts your health regen from food to be noticeably quicker(not much though)or a Survivor's Necklace,saves you from a single normally fatal hit every 5 minutes(ie:if a creeper would normally kill you in one explosion,you would survive with half a heart but the necklace's durability would be gone and would regenerate after a few minutes,allowing another survival).
I know ive said this many times but everything (nearly) should be more "expensive" in minecraft, as it is right now once you've found diamond you have basically finished, and are pretty much unkillable. what would be nicer is this to do after you have found diamond, ie thing which are there basically because they are fun, like slime blocks, or super duper ultra mega jump boots or the rainbow arrow etc...
Edited:
I was listening to the Phantom of the Opera soundtrack while rebuilding a Stronghold (I.E. replacing all the mossy and cracked bricks, putting in torches, etc) when I had a thought:
What if Jeb added ghosts to the Strongholds?
Preferably, they would be Metro 2033 style, as in faint silhouettes that drift about the Stronghold, softly whispering. Due to their transcendence, weapons of Diamond quality, as well as potions, would be the only effective means of combating them. Ghosts of Endermen, which would appear closer to the End Portal, would drop Ender Pearls, and Ghosts of Testificates would have random loot drops, such as picks, swords, etc.
When the Stronghold is properly lit, the Ghosts would cease to spawn, although during the nights, their whispers would still be heard across the complex occasionally...
what would be better is that nothing can combat ghost, you have to wait for them to leave of their own accord (maybe you could feed them, care for them, be nice to them and then they might leave???)