Agon/Irontooth dice pool style mechanic

MECHANIC 1: IRONTOOTH/AGON-ish

So I've been thinking about a potential Dice Mechanic that could be used in a Swords & Sorcery clone. It parallels the Agon/dice pool/Irontooth models I've discussed earlier in this blog. Basically, you roll a dice pool and retain only the highest and then compare it to a TN of some sort.

TIER DIE: This is a D4, D6, D8, D10, D12, or D20 based on your "level." The D20 is likely just for NPCs (deities and the like) at very high levels of play.

SKILL DIE: This is a D4 through D12 based on level of skill. Characters will be good at some things and bad at others.

BONUS DIE: Players can spend a consumable resource (let's call it "Fate") to add a bonus die into the mix. Some magic items, racial abilities, etc might also let you throw in a bonus die too from time to time (perhaps a Flame Tongue against an Icy Monster, or a Dwarf smacking a hated goblinoid).

GOOD THINGS ABOUT THIS MECHANIC:
- Simple, quick easy. No math required.
- Provides a "floor." All characters are likely able to attain some sort of minimum result because of the nature of dice pools, especially if they get a bonus die. Even an untrained character (the weakling mage with a D4 for physical combat) has a decent chance to succeed if he's of sufficient tier.
- Hard to stack. You can't really pile on extra dice/modifiers.

BAD THINGS ABOUT THIS MECHANIC:
- Hard to predict odds.
- Tops out at three dice. Once you add the third die, the average is already skewed strongly upward. Adding extra dice has little statistical effect other than ensuring that characters get max or near-max results every time. This is why Agon cleverly splits combat dice pools into an Attack Pool and Defense Pool.
- Low level, unskilled characters have no chance of attaining difficult goals. If you're rolling 2d6 and the TN is 8, you're hosed. This may be a good thing if you don't want low level mages to be able to even hit a very strong foe's armor. If the "fate" system allows one to add a large enough die then some success may still be possible.

An advanced version might address the topping out issue by splitting the pool into two somehow. Accuracy & Impact, Attack & Defense, etc. That would allow you to throw 3-5 dice into a player's pool, giving more room for modifiers, bonuses, etc.

MECHANIC 2: Dream Pod 9-ish dice pools

Another dice pool method could be using a pool of dice and retaining the largest. DP9 uses D6s; so, you might throw 3d6 and just retain the highest. There is a twist; multiple 6s add +1 to the total. So if you roll 4, 6, 6, the result is 7. One's skill would determine the number of dice in your pool.

A possible twist to scale it with 'tier' of play would be to increase the die size to D8, D10, or even D12. Thus, a 2nd tier challenge with a TN of 7 is still attainable by a skilled Tier 1 character who can chuck enough D6s to get multiple 6s, but its significantly easier for a Tier 2 character throwing D8s.

GOOD THINGS ABOUT THIS MECHANIC:
- Still simple and pretty easy.
- Also provides a floor.

BAD THINGS ABOUT THIS MECHANIC:
- Again, tops out around 3 dice. More than that is not really meaningful. This limits the relevance of skill levels and such.
- Difficult to modify, due to the 3 die limit. If you drop someone below 1 die, what happens? If you give bonus dice for whatever reason, it may be either very helpful (going from 1d6 to 2d6 is a lot better than going from 4d6 to 5d6).

ADDENDUM:

If you want more variability in your game, that's easy. Just add another die to the Dice Pool result, and add the average of that die to your TN.

For example, you could add 1d20+DICE POOL, and just tack another +10 on to every TN. That will make rolls highly variable, with chance being more important than skill.

You could also just add on a D8 + DICE POOL and tack +4 or +5 onto the TNs. That will make chance and ability roughly equal.