For those just coming in, this is going to be built on a previous post on a hypothetical resolution system of 3d6 (maybe +bonus) vs target number, with rich dice (dice that convey extra information). the dice respectively represent force, finesse and fortune.
The first thing to address is what this looks like in play. Even in the absence of mechanics, the dice can be useful for narrating an outcome. Just look at the highest die and use that to set the tone of the outcome. If the highest die is Force (representing strength and power) then that's easy: you land a hammer blow, you overwhelm the guard with your presence and you generally stomp on the problem. If it's Finesse (representing speed and precision) then t's equally easy: You find a gap in the armor, you subtly convey your point or you otherwise solve the problem with grace.
Those two are so clearly easy to envision that it's easy to not stop and think about Fortune. Because it's the most transparent concept (luck), and we know what luck looks like, we don't worry about it. But there's a danger there: describing luck is surprisingly hard. I mean, yes, it's easy to do a few times, but it gets very silly very quickly. The temptation, of course, is to describe luck in terms of coincidences. The guard just happens to slip on that puddle; the terrier just happens to fall on that guys head and so on. The more this happens the more it comes to resemble slapstick, and that's not terribly helpful for most games.
As such, the way to think about Fortune (and by extension, luck mechanics in most games) is in terms of opportunity. This has a number of advantages. First, it's much more tied to the situation at hand (falling terriers tend to be situation-independent) so it uses the color of the scene. Second, and perhaps more importantly, it makes the character proactive and keeps them at center stage. It's a small difference, but it's the difference between "The guard slips on a puddle" and "You drive him two steps back until his left foot is in the puddle, then take advantage of his bad footing to knock him down". The net result is the same (guard is on the floor) but the second sounds much more adventurous, and that's important.
I'm aware that this may seem like a sidetrack when compared to the mechanical possibilities of the system, but it's an important one. Coming up with a clever mechanic is all well and good, but if there is no clear way to turn it into the language of the table then it's never going to be anything more than awkward.
Ok, so with that aside, let's start looking at ways to start this idea some mechanical purchase.
The simplest model is to have some sort of bonus trigger based on which die dominates (which is to say, which is the highest). This could be expressed generically: If Force dominates you get a bonus to damage (or damage equivalent), if Finesse dominates you get a bonus to this (or maybe the next) roll and if fortune dominates, you can maneuver. That works, and it strongly supports the color of the dice but it offers very little in the way of player interface. This works roughly the same way whether my character is brawny or scrawny, and there's no way for me to make choices that impact this.
So here we have the first big fork: one way or another we want the impact of this to be responsive to player choice, but do we want it to be choices made during character creation (stats, skills), choices made in preparation (equipment, possibly spells), choices made in situation (tactics) or some combination of these?
Sounds like a good point to pick up tomorrow.
1 - This is actually a big factor, for good or ill, with 4e. By insisting on play with minis and maps, it changes the language of the table from one of description to one of 5 foot squares and numbers. In that second language, everything is very well written, coming together beautifully. The problem comes when you try to translate from the tactical language to the descriptive one: the guidelines for doing so are quite faint indeed.
2 - The term "dominates" is from Don't Rest Your Head, so it's very natural to me, but it could easily be changed to suit the tone of whatever the final game is. If you're feeling really nerdy this is a great place to put in one of those made up words that makes a game sound EVEN MORE dorky.
3 - Fortune might merit a switch to something more setting or situation specific, but that's easy. It's a wild card, and there's usually an obvious use for such a thing.