I kinda liked the Force Die in SWRPG, even though the way it was used could lead to some wonky effects. I even had a mental sketch to incorporate it into a Savage Worlds conversion of Dark Sun. In Savage Worlds, spellcasters use Power Points (PP) to fuel their spells, and I liked the idea of sorcerers rolling Force Dice to generate PP. Any white pips came from your own strength, but to use any black pips, you have to drain the life from the land around you (sorcery is the reason the Dark Sun setting is a barren wasteland).

I had guessed that Genesys might use some sort of point-by-point system for generating magic power. And I was wrong. But I still like the dice.

So let's say you were playing Genesys, and you like the idea of the Force Dice, but you don't want to build big spell trees like the Force Power trees in SWRPG. How would you do it?

Use the spells as they are, but the required number of Light Side points is whatever the Difficulty would have been. So a 3 Difficulty Spell requires 3 Light Side to be successful. Excess pips can be either more success or treated as Advantage.

To convert Dark Side to useable LS pips requires a Story Point plus a number of additional Strain equal to DS used.

the number of force dice rolled could be based on ranks in a skill, or a characteristic.You could even add a 7th characteristic just for Power, spellcasters could automatically start with 1 in it, with the ability to spend starting xp to increase it.

or you could make it a Talent to learn

Spell Caster:

Tier: 1(or 2), Unranked, Passive.

Effect: You can cast spells, your Spell Power Rank is now one.

Improved Power:

Tier: 4(or 3 if you want rapid progression), Unranked, Passive.

Effect: Your Power Rank increases by 1 for each rank of this talent.

Build a Genesys Spell as in the CRB, but split the effect Difficulties into a Complexity and Magnitude.

Complexity -- how complex/difficult it is to cast the spell

Magnitude -- how big/great/ranged/extended the effect is

you use your normal skill roll with Complexity as Difficulty.

Magnitude is the number of white power-pips you need to generate

Spells from the Official Books have a Magnitude equal to half its Difficulty rounded up (eg from RoT)

if your casting roll is successful you can still aim for a smaller effect by dropping effects from the spell equal to their difficulty-pip cost.

power-dices must be commited to over time effects that require concentration, replacing the concentration rule.

Strain Variant:

you gain one power-die (ie. Force die) by expending one strain, you cannot expend more than your casting skill in strain per round.

Characteristics Variant:

you have a 7th characteristic called Power which represent the number of power dices you can use each round without expending strain/wounds

Power characteristic starts at 0 and must be paid for as a normal characteristic, it is the same for Arcane/Divine/Primal/Psionic/etc,
as it represents the actual amount of mystical energies your pcs body is able to conduct without suffering.

I know most of these responses are trying to convert magic into using the force die in some way, but i actually came up with a way to include them in my custom setting Gentlemen of Fortune: Fantasy on the High Seas . My players and i didn't want to buy new sets of dice when we already purchased so many for Star Wars. It felt weird to just not use them. So i came up with a new mechanic inspired by something from the FATE system. Without going into excruciating detail...

I call it Rolling the Bones. The basic idea is that if a player fails a check they can choose to succeed instead. They have to flip a story point and roll the force die. Based on the results the GM selects something the character must sacrifice to succeed. White Pips mean a less severe sacrifice , black pips more severe.

I've been thinking about using them just to determine starting Story Points.

I've been using it for a Dark Sun game I'm running to simulate the Defiling/Preserving mechanic. I blacked out an additional white pip, since Defiling is by default the easier of the two. Any spell cast rolls the Force Dice along with it. Black Pips allow for "Defiling" and can be spent as either Advantage at a one to one or as Success at two to one on the spell. Yes, this means spells have a ton of Success at times, but it also moves characters along a Defiling track similar to the Dark Side one and has massive story consequences. Meanwhile, Preserving returns an additional 1 Strain after the Spell is cast per pip. It's rough and I'm going to be tweaking it, but it hits the dichotomy of casting in Dark Sun well.