Well, this is something I have seen recently in the Wotc forum as well. The first reaction was a massive knee jerk, especially the soul using part. Although that feature might have been used in homebrew games. Like the voices of dissent there and here. I too, have many misforgivings on it.
For one, how would a soul will be considered to have a stronger essence from another.
Does it deal with taking from Elves also, they don't have that catergory of a soul. They are spirits wrapped in flesh.
I do understand in fairness, that the magic system is suppose to grow in earnest. But to me, it is still lacking in some areas. And my biggest pet peeve is the component using for spells. I do know also that there is a feat that negates that too...to some degree.
I know it is a lot a record keeping, but shucks...it would be interested to see, how many time a spell can be casted within a certain amount of time, before the components of it use, are exhausted. It will mean a better part of thinking more carefully in what can be used for what situation.
I guess the big pet peeve question is, how much components can be carried, used, before that specific supply is gone.
I surmise that some DMs do this, but this is not carried over in the Wotc thinking, if it was at some point. The first thing or last voice would have said, it will slow things down for the wizard, druid, cleric, ranger, and Paladin...can't recall right away if the sorcerer is affected as well. In doing their castings.
Honestly...as it was said before, it would make things interesting, on what can be casted, with what is on hand on in supply.
But these days, with new and newer feats coming out...components use, especially for the wizard, druid and cleric profession is slowly becoming...obsolete.
Which is a shame...I do say.
Like Psion, I like upgrades in magic...but like Buttercup and few others...I grow wary of more materials to absorb...more info to cram into the brain, more adjustment to a system, that is simply...still flawed.
Oi.