Not completely true. Advantages and Disadvantages is inherent trait that one can put themselves to be strong/weak as certain parts right at the beginning of the game, in which I assume the perk in talking involve leveling up and obtain certain ability through this (alias Fallout). For example, I can make my self resistance to magic but I have to "equal" or balance it out by either making myself have the ability to burn be in the sunlight, not being able to use a certain type of weapon, and/or become afraid of a certain type of monster. Its basically customizable Birthsign System/Trait System on steroid.
If one want to have a good idea of what http://www.uesp.net/wiki/Daggerfall:ClassMaker#Special_Advantages and http://www.uesp.net/wiki/Daggerfall:ClassMaker#Special_Disadvantages, just click the respected link.
Yes advantages and disadvantages was cool, however I mostly used them to gain advantages myself. High elf with critical weakness to paralyze, not allowed using orcish armour; high elfs was immune to paralyze and orcish armour was rarer than daeric.
The problem here is that most players would use it to exploit and/ or wreck their character.
But it had been cool as a design your birthsign tool.