I like the SW: EotE dice mechanics as well as the older d20 dice mechanics so I was thinking is there a way to merge the two? Basically recreate a narrative dice experience with a d20 system.

First question many of you many have is why? My answer is that there are elements of other game systems that I like that don't exist in EotE and also because I like mixing and matching stuff.

My initial idea is when making an attack or skill roll you roll 2d20 and one of them will be your normal success/failure roll (I will call this the resolution die) and the other die will be your advantage/threat die (I will call this the narrative die). You can either pre-designate which is which or possible you can decide after rolling.

The resolution die would determine success or failure determined by the rules of the game you are playing. The narrative die would determine whether an advantage or threat happens. Whatever target number you needed to meet to succeed or fail could be the same target number you need to have an advantage or threat (i.e. meeting the TN would mean an advantage and not meeting it would mean a threat).

One issue with this is that the chance of a success and an advantage go up and down together. This is different than the EotE narrative dice where less success means more advantage is likely, and less failures makes more threats likely.

Another issue is how to handle triumphs and despairs (if you want them). Maybe add a third die to determine that? Maybe only if you get a 18-20 on this third die would you get a triumph and a 1-3 would give you a despair (the exact numbers you use would depend on how likely you want them to be). One issue here is that you couldn't get both a triumph and despair at the same time.

I would probably not use a third die and skip the triumph and despairs.

Advantages could possible give you combat advantage or temporary HP in combat, or bonuses on you or an ally's next check, or handled narratively.

This is probably a crazy idea but I thought I would throw it out anyway.

Any other ideas?

Another idea is that with the normal d20 you roll a number of Fudge dice based on level and each + equals and advantage and each - equals a threat, and they can cancel each other. Then you spend the net advantage or threat.

I probably wouldn't use this with standard 3e or later D&D edition since there is enough going on each turn already. However, this narrative dice hack may spice up older editions oh D&D (or a stripped down version of 4e that I have used before).

I'd just replace the d20 with the FFG system completely.

Use d20 as the base, but rather than conditional modifiers, add narrative dice to the role.

In addition, keep an open die pool (established similarly to Destiny Points in this game), that the PCs can dip into whenever they want (each success = +2)... but then they pass to the GM for his use.