I recently posted some thoughts on handling large-sized characters in 5th Edition D&D. I was also thinking about small-sized characters (and tiny, and so on). I’m certain that the decision was made for the purpose of simplicity and balance, but reading through the 5E rules I did think that too little was made of the advantages, and disadvantages, of being small. Especially small in a D&D sense, where you are shorter than 4 feet and weight maybe 50 lbs. Most halflings, and many gnomes, are smaller than my 6 year old daughter. Different build, more lean muscle mass, and so on, but still. She is not large.
In the rules as written, small creatures take up the same area on the battle map, have the same class hit dice if they have a class, etc. Small creatures with no character class have hit dice one die type smaller than medium creatures. I know that small creatures can use Acrobatics to move through the space occupied by a large creature, which is cool, and they have some weapon restrictions. They are also able to theoretically squeeze through a tiny space, whereas a medium creature can only squeeze through a small space.
Now, if I wanted much more detailed rules on size, I would just go back to 3.5 or Pathfinder. And no worries there, both are great games I’ve played many times. But what I would like are a couple of small changes that make the choice to play a small race more meaningful.
I’ll start with what is likely my least popular idea – I think that PCs should follow the rule of monsters and small races’ class dice should be downgraded one step. I think that the actual effect of this would be mitigated in a number of ways. First, any PC casters who are a small race will often have one primary stat and then can easily put their second highest score into Constitution – this is especially true of sorcerers and wizards. Bards and clerics have more to worry about, on average, but can still be quite tough if they wish to be.
I think that in general, size should be taken into account when rolling Dexterity (Stealth) – one size difference granting someone advantage on the roll. This would mean that small characters sneaking up on medium characters or larger would automatically have advantage, and it would add a house rule that would make it easier for all PCs to sneak up on ogres and giants and the like.
Cost of living
It makes sense to me to cut the cost of living for a small PC in half. They can get along with less living space, much less food, less water, and so on. Their clothes take up half the material or less, and all of their tools are small-sized, or can be. This makes a small difference, but makes sense to me.
Here I’m going to just steal from Pathfinder/3.X and give small PCs a +1 to their Armor Class. They have about half the surface area to aim at, can more easily take cover, etc. This also helps do a little to balance out the loss of 1 hit point per level, on average.
This got me thinking about tiny PCs, like player-character pixies and sprites and quicklings, which sound cool. For them, I would reduce their hit dice by yet another step, also reduce their weapon damage by one die type while keeping the restrictions for small characters (being stabbed by an inch-long knife is just not that scary). I would divide their cost of living by 4 and give them advantage on Dexterity (Stealth) rolls to sneak up on small or larger creatures. Tiny intelligent creatures are also often balanced out by having super-speed or the ability to fly, like the examples above, and perhaps more innate magic than is normal. I’d want to see this in a game (someone playing a pixie, sprite, quickling, etc.) but I’d be open to the idea. They would also get an additional +1 to their AC.