Mithras having a constant +25% movement speed (assuming 5 possible upgrades), are you insane? Even 10% would be terribly imbalanced. Yes, I am a mithra.
If race dependent merits were to exist, I would rather every race would get the same merits, but some races would need less exp to max out certain stats (and vice versa), with humes having no bonuses or penalties to any of them.
Of course, these differences would only actually be worth mentioning if the new merit categories required retarded amounts of exp per upgrade. Like like 50k Ultralimitpoints for each ultrameritpoint as the baseline, with like galkas only needing 2 ultramerit points to increase the HP bonus to the first level, while tarus needed 4.
Honestly though? I think the races are different enough as it is, we don't need to elaborate even more on that. If anything, I would just want more amusing, neat, and cool race dependent stuff that didn't really make a difference in serious endgame content. Like mithras dealing slashing damage instead of blunt when fighting without a weapon.