I had several thoughts on this subject while explaining to someone at the game table why halflings got a bonus to both AC and attack rolls.
1) Small size also provides a bonus to Hide checks. Presumably this is because halflings, to a human, are smaller and therefore harder to notice. However, going by the same logic that provides halflings with both AC and attack bonuses, a halfling should also receive a bonus to Spot. Actually, strike that: All races should get a bonus (if smaller than Medium) or penalty (if larger) to Spot checks equal to the bonus/penalty their size provides them with on Hide checks. Two members of any race, regardless of size, should be able to have the same chance (barring racial bonuses to Hide) of spotting each other as any other race. As it stands, giant rogues are likely not very successful, and pixie rogues probably surprise themselves while shaving. If they shave.
This also makes sense from the perspective of an individual. A halfling is more likely to notice a skulking human than the human is simply because, from the halfling's point of view, the human takes up twice as much of his field of vision. Replace "skulking human" with "lever to open the human's secret passage", and you've still got a viable reason for size-based Spot bonuses, because a halfling would have constructed that lever smaller. To the halfling, the human's lever is much bigger than it should reasonably be, and he has a much better chance of finding it.
2) This arose from the same discussion, and is less game mechanics than it is flavor. I'm putting the main idea in italics: A society's regulations and restrictions on magic are inversely proportional to the race's size. Think about it: For a giant village, a fireball isn't going to cause as much devastation as it would in a human village. The damage is the same, but the fireball of a giant is exactly the same size as that of a human, and that radius looks a lot less village-devastating when you're trying to cram giant huts into it rather than human-sized huts. Giants are likely to have relaxed attitudes to magic, simply because it's not as effective at their size as it is for humans, at least in terms of range and area. The reverse is also true: A village of pixies would be terrified at the approach of a spellcaster, who could probably set the entire village aflame with a single fireball. And while the range of, say, finger of death is the same when cast by pixie or giant, the range looks a lot more impressive when you're about two and a half feet tall. Thus, smaller races are more likely to put restrictions on magic, taking steps to do so ranging from confiscating spell components at the gate to having an antimagic field in important areas to outlawing spellcasters in general.
Of course, you could scale spell sizes to fit the caster, but that opens up a can of worms that would probably be large enough to create a scale model of Kyuss. And then there's the argument that there are very few giants who become wizards, but the argument still stands.
Any thoughts or comments on this?
tl;dr Give races a Spot modifier equal to their size-granted Hide modifier, and giants think magic is less scary than humans think it is.
