i have an idea for a new game with all new races. most of the races are simple enough to make by modifying PHB races as the DMG suggests. the races in the game are animalistic. originally i wanted to make one race for each of the following: mammal, reptile, fish, bird, insect. i actually ended up with ideas for two bird races, two mammal races, a fish race, a reptile (amphibian really but who's counting?) and an insect race.
anyway one of the mammal races is based on bears. so i have these bearlike humanoids. i have ideas for temperament and society and some ideas for racial abilities and modifiers. i'm thinking bonuses to strength and con, penalties to intelligence and charisma. the intelligence penalty is not because i think real world wild bears are stupid compared to other animals. its more that the bear race is more animalistic than the other races, and also to balance the two bumps to physical stats.
i dug through the rule books and didn't find anything useful on balancing a large race. there's not a whole lot about making new races to begin with (everything in the dmg basically boils down to alter standards or try and copy the standards as closely as possible which is kind of paltry as guidelines go). as far as i can tell from what i've scrapped together just making a race large would grant the following: +2 STR, -2 DEX, -1 AC, -1 to hit, +4 to grapple checks, -4 to Hide checks, 10 space, 10 reach
all that seems like a net benefit to me which means taking a standard race and adding all that would make an unbalanced race. at the same time i don't think that's enough to balance it with other races. the concept for the race is that they are bearlike. i could grant an additional +1 racial bonus to grapple. but that would give first level characters of this race a huge advantage. if the player rolls up a fighter with 12 STR (before the bonus) you'd have a first level character with a +7 grapple check. there would be practically no reason not to grapple everything. that alone makes me think it might just be a broken idea.
one of my ideas was to make the race medium sized (on the large side of medium, like half-orcs) and allow players of that race to become large (permanently, basically they grow larger) by taking a feat. but it seems more powerful than a feat too. i could split it into two feats. level one they start to get bigger, +1STR, -1DEX, +2 Grapple, -2 Hide, 10 Reach. second level they get the rest. not sure i want to go that way and i don't know if splitting it into even two feats is balanced. it's hard to compare to existing feats because not all feats are created equal (imho). if i split the large size into two feats and make the pre-req for the first level a minimium level of 3, that means the player wouldn't have a full fledged large character until level 6, and by then i think it would work better.
another idea i had was to make only females of the species a playable race. the idea i had for the race's culture was that they were matriarchal. all their communities are run by females. children are raised almost exclusively by their mothers and the males tend to wander. basically i took what i know about bears (not that much to be honest) and tried to think of what they would be like if they were as intelligent as humans and had the ability to make and use tools. the females who are interested in raising young would realize that there's safety in numbers. they'd band together, set up communities, raise their young. male bears, real ones, don't associate with other bears unless they're killing them or mating. from what i've heard, like i said, i'm not an expert. i don't need to be, i'm not writing a documentary. so anyway i figured the males would wander on their own. they'd be hunters, foresters, miners maybe. mercenaries. that sort of thing. they come to town to trade, get laid, and then they fade (sometimes they raid. they like to play spades. and they love a parade).
so i COULD say the males are big, scary, mean and Large and only in the game as NPC's and monsters. the females could be smaller, medium sized, and balanced with other races. but as soon as i say "this is a race where you can only play a female" i know someone will want to play a male. this is assuming i ever even use the race. i probably won't get a chance to run the game but i like thinking about this stuff.
i think my best bet is to make a balanced playable medium version, split Large into two feats, limiting availability of the first level of it to characters of minimum level 3. i had an idea to make feats exclusive to certain races so that would be consistent with the other ones.
incidentally, in case you care, the other races are based on wolves (tribes of rangers), roosters (small but tough, favored class fighter), storks (tall spindly mysterious mages), fishy men (fishy... men), bees (missionaries, obsessed with order, city builders, favored class cleric), and frogs (swamp dwellers, followers of the old religion, not fans of bees' civilization, favored class druid or bard).
I have other ideas and may post more later but this post is long enough and i'm bushed.