One idea I've been considering lately for the Dawnlands' mechanical realisation is simply not distinguishing one PC species from another by their attribute averages and ranges, or by attribute minimums required to play them.
Normally in MRQ2 / Legend or Openquest, you have seven attributes, which are generated as follows:
These are meant to be rolled whenever you create a human character, especially a PC. Other species have different dice counts for each stat, so dwarves in MRQ2 / Legend are:
Dwarves also receive the Earth Sense and Dark Sight traits beyond this.
Trying to figure out a system behind these attribute distributions is an exercise in frustration, as there does not appear to be one. The result of this is that when you're coming up with new species, or changing old ones, there is not a clear set of principles or ideas to follow. You're left eyeballing distributions, checking averages, and then trying to decide what is "fair" and what won't cause everyone to shift over to playing it. Sure, you can talk things over with your players beforehand and make declarations about staying on theme with a human-dominated world, or you can try the pernicious and misleading strategy of insisting that there are "social penalties" a character will face as a non-human, but none of these help me, since neither is true in the Dawnlands. I'd rather design things from the start so that there is at least rough parity between the available choices.
PC Species in the Dawnlands:
Half-dogmen (half-gnoll, half-elf, technically)
For a total of twelve races or species, counting the mixes. Then, there are perhaps another 4-6 types of humanoids who are not suitable as PCs, but would be common enough that stats for them would be extremely useful (Lizardmen, kobolds, goblins, and murder gnomes come immediately to mind).
I originally drew up a document statting out all the various differences based on the physical, intellectual, etc. qualities these races and species should have, but it was an incoherent mess and I've since disowned. it. The main problem was the SIZ stat.
My initial plan was to divide all three groups into "tiers" by SIZ, with small, medium and large species and races. However, the tiering broke down because there's an uneven distribution, and some unclear edge cases. Do dwarves count as a small race? Do half-dogmen count as a large race? As well, categorisation of some individuals, particularly individuals in the main group the PCs come from - the Kadiz nomads - is unclear. Most have at least some elvish descent if human, or some human ancestors if elvish, and I was trying to figure out what the blood quantum should be to qualify as a "half elf". In the end, I abandoned the entire project as fruitless and overly complex - almost unplayably so, as it would be difficult for people trying to figure out what species to play to make that choice in a straightforward way.
The idea I'm coming around to is that everyone, everyone rolls the human stat line. You rolled SIZ 18 for your halfling? Well, he's a fat, muscly bastard. SIZ is technically a measure of mass, not height, which allows this sort of thing. Your gnoll has SIZ 8? Then he's a scrawny, underfed mutt of a gnoll, maybe the runt of his litter. This has the advantage that PCs don't have to memorise how attributes are rolled for multiple species.
Originally, I was concerned about giving dwarves infravision, and gnolls smell powers and all that stuff, but I've finally decided that I don't really care enough to, and will simply roll it all into already existing skill checks. When the dwarf uses his infravision, he is just making a Perception test in the dark.
I like this solution because it reinforces a couple of core themes of the Dawnlands setting. The first is the idea that almost everyone is "people", regardless of how horrific and weird they look. Common stat generation reinforces that idea by suppressing arbitrary special difference. The second is hybridisation and recombination. Most people in the Dawnlands are some mishmash of human, elf, dogman, orc, etc. to varying degrees, and sorting that out into arbitrary categorisations based on blood quantum with a certain threshold determining when you get the magic powers leaves a sour taste in my mouth.