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Kill 5 People (20 shifts a piece)
I like the ideas posed above for having a character's "value" (their number of consequences, and thereby their plot importance) determine the amount they provide to a ritual.
The problem with the making sacrifices who're nameless count for less is, well, in-universe, what makes Lt. Murphy a more potent sacrifice for a particular spell than the nameless Lieutenant heading up Homicide? It's kind of implying that a named character's life is worth more than the extras. I kinda like the idea that stopping Evil McBadguy from sacrificing a random innocent victim is just as important as saving Lois Lane.
That depends-- is the ritual using Lt. Murphy
targeting Dresden (or someone who cares for her)? Or is it targeting someone who
doesn't know Lt. Murphy?
Sure, the average joe is as important as Lois Lane-- but not if you're Superman. If the ritual is
targeting Superman, using his love/girlfriend/wife (depending on your story arc)
would reasonably add more to the ritual in-question. There's a metaphysical connection there.
Also, there should probably be diminishing returns applied. The first sacrifice is worth the most, each one after it is diminished by 10% or what-have-you. That way, you never reach a point where killing additional people is pointless, but it becomes necessary to kill more and more people to get the same benefit. See: Chicken Pizza.
Kill 50 Animals (2 shifts a piece)
This should, wihtout a doubt, suffer diminishing returns.
Make 30-50 decelerations and sacrifice yourself up to a severe.
Seems legit... but I do think a set of general guidelines should have been worded into the RPG about limiting the number of times each character can use each skill for declarations. Or imposing diminishing returns on those declarations. Or imposing ever-higher difficulties on the successive declarations on the same skill, showing ever-increasing difficulty of getting high enough quality components or whatever.
Spend 99 scenes doing nothing.
I think people misinterpret the developers' intention with the "sit out a scene" option-- and I honestly wonder why. Of all the stuff in DFRPG that isn't spelled out explicitly, I seem to remember there being a couple paragraphs or even a whole sidebar on when this is and why it isn't appropriate. It seems like it was intended more as a "I have 1 or two odd shifts left and we need someone to run for pizza anyway. Rather than sit here and figure out the 20th convoluted way I can augment my abilities, can we just say I finish it while I'm gone?" and not as a "Haha, I can simply join the game two years into the campaign as an unstoppable, ascended deity!"
Finally, as others have already pointed out, your interpretation rewards people for un-fun. Sitting out is un-fun. Don't allow it.