In issue #2, I posted my list of modified bonus types. In that list, two of the most used (and abused) types are gone: inherent and size types.
The first is gone because in my homerule bonuses and penalties only modify rolls or DCs, so a bonus type that only applies to ability scores is useless.
The second one is gone because size as it is in the standard Pathfinder RPG is no more in my games.
Usually, sizes above or below Medium generate tons of modifiers, require tables of conversion, and a lot of other stuff. This, for example, hampers creating new monsters, changing form to a differently-sized one (look at the rules for the Polymorph subschool), having weapons for different sizes and spells with the same effect no matter what the size of the caster, and so on.
Thinking about it, I noticed that all this stuff isn't really necessary. No modifiers to ability scores, no extra HD, no modified natural armor, nothing. You only need to modify maximum load, damage, attack rolls, combat maneuver checks, and STR and DEX based skill checks.
So, I came up with this variant rule:
- You get a -2 to attack roll for each size of difference between you and your target, both larger or smaller.
- The damage you deal to a larger creature is halved once for each size of difference (half for one size larger, one third for two, etc.), while it is doubled if dealt to a smaller creature.
- If you are larger, you get a +5 to combat maneuver checks for each size of difference against a smaller foe. You also get that bonus to CMD. No need to modify anything if you are smaller.
- You get a +5 bonus to STR-based skill and ability checks and a -5 penalty to DEX based skill and ability checks for each size above Medium.
- Carrying capacity already takes into account larger or smaller than Medium creatures, so no need to change anything here.
This set of rules requires work, because it's required to remove all the size modifers that are present in the game, the extra natural armor, the extra HD, the weapon conversion tables, and so on.
Simply said, larger or smaller creatures are built just like standard Medium ones, with the same base scores, the same number of HD, the same Cos or number of HPs, the same base damage, etc.
What governs how many Hit Dice they have is their CR.
Normally, a NPC has a Challenge Rating of Level -2, but most creatures are weaker than that, much like a commoner NPC, so they should have a CR of Level -3.
This means that creatures have the following HD/levels:
Commoner or "average array" monster - CR+3 Hit Dice.
NPC or "NPC array" monster - CR+2 Hit Dice.
PC or "Heroic array" monster - CR +1 Hit Dice.
To this, you just add 1 HD per size below Medium or subtract 1 HD per size above Medium. Recalculate the creature's stats from that.
As always, if someone already posted rules similar to these, please feel free to add a link below. Comments and feedback would be appreciated.
Keeping Str (and Cos, and Dex, and HD, etc.) as a reflektor of size has some drawbacks, though: a larger creature would have really high attack and save bonuses, even higher base damage (due to the fact that a high Str score rises both the minimum and maximum damage), nearly impossible to beat CMD, and so on. Also, it would still be susceptible to sudden death through massed attacks by a team of smaller creatures, which is one of the issues that players have had in 20 years of d20 games with huge "solo" bosses, because it would have no damage mitigation coming from size.
On the other end, small or smaller creatures, even with a lower Str score, could become even deadlier with their enhanced Dex score, especially with Dex-based classes like rogues, slayers, gunslingers and some investment in finesse combat. I always found rather annoying that a halfling rogue could one-shot a huge or larger dragon with a dagger the size of my pinky, or that to give a larger-than-Medium creature a chance not to be hit by smaller crestures it would be necessary to stack unbelievably high natural armor bonuses.
Let's say that with this homerule I try to make things a bit more realistic: hitting creatures of different sizes is more difficult (either because they are smaller and more agile targets or because their size makes smaller weapons less effective), being hit by a larger creature still hurts (even if their attacks have a lesser chance to hit you), smaller creatures have to team-up to confront with a larger foe and to use appropriate weapons and strategies, etc.
At the same time, creating monsters of larger or smaller sizes than Medium becomes much easier, and so advancing them or changing form into one of them. A GM would have less troubles with shapechanging characters in their games.