Sorry for not being very responsive - as you can see from my signature, the haze is back before I could fully recover from my flu.
I'm quite behind with all my posting due to the delay, so please be patient with me as I try to catch up as fast as I can.

Anyway.

[quote=@Stern Algorithm]I think the 'progression of sin' makes sense.[/quote]
This. This has to go into the lore notes. >:)

[quote=@Stern Algorithm]If we limit it to just wrath, what are your thoughts on how we differentiate the characters? I suppose rather than the elemental differences being tied to the sins, they would be tied to the individual Rias themselves? The Rias themselves would have a wide array of differences with respect to the powers they impart on their hosts. If we go with that, would we want to theme the Rias in a certain way as an added layer in addition to them being fueled by wrath?[/quote]
I've been experimenting around the thought of: what are some of the most basic/fundamental causes that trigger the hatred of one to desire revenge obsessively? Note that all these 4 can be interchangeable in certain situations.

[list][*][i]Betrayal[/i]
This should be obvious enough and I won't elaborate too much - I mean, anyone would consider a painful payback to the person who tramped over your trust for him/her. Can be stemmed from lust.[/list]
[list][*][i]Lost[/i]
Can be either loss of someone or being stripped of things one deserves. May be tied in with pride in some ways.[/list]
[list][*][i]Longing[/i]
This is a bit different from the sin of envy: while envy is the obsessive desire for something one does not have, this cause is more of a generic desire for something - from envy to greed to gluttony.[/list]
[list][*][i]Insanity[/i]
This should be self-explanatory.[/list]
We can have the Rias tied to these 4 'causes', which also fits with our four-character team we're going with.