Only specific accessories have been converted into cheat items. See below:
Superb Belt of Magic Defense
Superb Ring of Attack
Superb Ring of Armor Penetration

 -- When you use this mod, it is highly recommended that you do not use any amulets at all with Friendly Fire turned on. I've tested this with Superb Ring of Attack (900%) damage. It destroys amulets, no matter what. No way to bypass that. I've tried "Take only one 1 damage from all attacks but health lowered to x" and "On dying, x% chance to heal for half health". Both of them cause game crashes, and I've tried everything, such as re-creating duplicates. Nothing works so, this is the best option I can go with, without causing any game crashes on anyone's PCs.  --

For more details, see images. 

Personal use, to be honest. I'm just sharing this here. I've double checked everything, Added as much I could to get working, having run through multiple tests. The effects as you can see in the images are the ones that worked the best together. 

Update
Main file:
1.0 - Initial release
1.2 - Skipped 1.1 since I did significant changes to this mod. Removed Superb Amulet of Willpower, reverting it to normal item. Moved Cold, Electrical, Fire, Spirit and All Damage resistance to Superb Ring of Armor Penetration and Lifeward Heart & No Physical Effects moved to Superb Ring of Attack. 

If you're researching this mod on the provided project file, you can review some of the stats and abilities I've put in and tested. Mind you, not all of them will work.

100% cooldown:
1.0 - initial release

Prologue Additions:
1.0 - Initial release

With the above converted accessories, you'll be doing a lot of damage and it's extremely unlikely that you'll be dying to anyone.

If anyone wants to mess around or make their own versions, the .fbproject is also included for your own investigations as the only application I've used was Frosty Editor to make this mod. 

-- Installation instructions --
After downloading this mod, you can click the .rar file and drop it into Frosty Mod Manager for easy installation

-- Uninstallation instructions --
Select this mod in Frosty Mod Manager and select "Remove mod(s)" for easy removal.

Optional: 
100% cooldown
Cooldown limit raise mod included as an option. If installed, raises the cooldown limit from 90% to 100%, enabling instant cooldowns on your spells after casting them, when using items such as Superb Ring of Attack (includes 100% cooldown modifier)

Prologue Additions:
Adds 10 cheat accessories to the first corpse you encounter in Prologue, making it easier for you to equip your character and all 9 companions from the beginning.

Note:
About -100% cost modifier, it will show as red. It's fine! Don't worry about it. It will actually reduce the your mana/stamina cost by 100% enabling free spams. If you put it in positive, meaning 100% cost modifier, it'll just increase the mana/stamina usage cost.

Recommended mod to pair with this mod:
https://www.nexusmods.com/dragonageinquisition/mods/3373 - Has all the above listed accessories in the shop, plus it only costs you 1 gold each for any of them.