So I got time to build a fast mock up of what I'd like to see. Basically, it's a build builder like we got for ME3 MP but adapted to your style and DA MP.

It all depends on how much time you're willing to make, so I think you should go in phases.
Phase 1
- Add a section with the base stats at the left
- Resize all icons to 85% so a full skill tree can fit in a 1980 x 1080 window
Phase 2
- Add some interactivity to stats
- Promotions affect the values displayed for Constitution, Cunning and Willpower
- Abilities and Passives affect the values displayed for all appropriated stats
Phase 3
- Display equiped items
- Move up the section with the selected abilities (bottom right) and use the space created on top of "Feedback - Changelog" to add 7 combo box (Main hand, Off hand, Armor, Belt, Amulet, Ring 1, Ring 2)
- To avoid a combo box with hundreds of entries, only define the unique items and use a single entry for "common" and "rare"
- Hovering over a small icon next to the combo box would show the item stats in the top left sections (like abilities and passives do)
- Equiped items affect the values displayed for all appropriated stats
- A new section should be introduced below the stats to show the "Special abilities" like "10% for walking bomb at 50% damage" and the likes
Phase 4
- Allow players to modify the stats of equiped items
- Add a button next to the combo box to open up a new screen
- The new screen would display relatively the same stats as the left section of the main screen (the stats I added in the image) but with input boxes so you can change the values to correspond to the item
- The new screen would also allow you to select the special abilities (10% walking bomb, etc.) on checkboxes, which will be displayed in the section added on phase 3
- Don't waste your time trying to implement crafting or runes, we can simply enter the correct value directly instead
So when can we expect the changes? Haha, I'm kidding, I'm kidding... or not 
In any case, this would give us all the tools to actually check everything we could ever need for DAMP. I'm guessing any new content will require some work to include in the screen, but the structure would make it relatively "easy". It's a tall order, that's why I said this would depend on how much time you're willing to spend on it. It's also why I suggested "phases", each one being less important than the one before them. As far as I'm concerned, I'd be more than happy with only phase 1 and 2 but I won't stand in the way if you want to do more...
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