I also really like the idea of the 'weakness' aspect of other races changed into something more along the lines of the vulnerability, but using the damage type and not the metal to determine how much damage might be added. I think the amount of damage added of course needs to be looked at in great detail, but it's better than increasing the critting ability as much as the weaknesses do.
Currently enhancing criticals is used as racial weakness, which is what fuels Minstrel's post above. I don't think that all racial weaknesses should be changed (for instance, a forest-troll should burn heartily and not merely take more damage), but some could easily be changed to material allergies or vulnerabilities. I am not interested in making these damage type dependant rather than material specific for two reasons: damage types are easily molded to whatever forms desired, and material weaknesses are already supported.
Without having tested, or even looked at the code, I can assure you that vulnerabilities are more scalable and controllable than the damage-type specific weaknesses we currently use for races. I would like other ideas to look at though, if there are any. (Minstrel has notably left out potential "less extreme drawbacks")