The push for more causality-based systems is indeed a trend around here, but I think a more stat-oriented build can also implement causality. For example, instead of applying stats to the characters themselves, you apply stats to their equipment, thereby influencing the tactics that go into using that weapon. To illustrate, let's say you have 4 stats for weapons in a fantasy RP: Type, Weight, Enchantment, and Material. Using these 4 stats, a steel longsword enchanted with light magic can be represented as such:
Type: Sword.
Mass: 4 (hypothetical value).
Material: Steel.
Enchantment: Light.
Then, you start determining things like damage output and ease of usage from those stats.
Let's start with the weapon's Type, which can influence things like how well it does against various forms of armor, as well as what weapons it can defend/parry against most easily. If we were to go by rules of the "weapon triangle" in Fire Emblem, then the sword would do better against axe-wielders, but not as well against someone with a spear. Since the greatsword is a weapon that can be used for stabbing as well as slashing, it would do equally well against most forms of armor.
Next, let's consider the Mass, which constitutes both size and weight. If we assume a Mass of 4 is heavy (for illustrative purposes, let's assume the heaviest weapons have a Mass of 5), then we can deduce that it is a slow, but powerful weapon. The weight also makes it more difficult to wield, but the blade's size allows for wide-sweeping attacks that can damage multiple enemies in one blow. Naturally, this weapon would be most useful against slow and/or heavily-armored targets, but its effectiveness against more agile opponents is less so.
Third, let's discuss the Material. Steel is stronger and harder to bend than Iron, so it can take more abuse without needing repaired. However, steel is also more expensive to produce, so repairing it at a smithy would cost more. In terms of its usability, this one basically comes down to "how much abuse does the player expect it to take?"
Finally, consider the Enchantment. This is where magical affinities come into play. Let's say that a Light-based enchantment will make the weapon more effective against Dark-type enemies, but weaker against Elemental-type foes. Judging from this, combined with the previous stats, one could assume this weapon would be most useful against a full-body-armored "Dark Knight" opponent, especially if said foe was wielding an axe.
On the subject of that "weapon triangle" thing I mentioned earlier, word has reached me that Paradox is planning on what could be a Fire Emblem RP. If he's still planning on that, he may find what I babbled on here to be useful...but who knows?