I don't think you'd have to worry about that particular juggle at all. The third law pretty much rules that sort of thing out. You could go for a defense on the grounds that your target wasn't human I guess but that's one where I could really see wardens extending it to include more than just mortals. In fact that's exactly what was going on in the discussion with Morgan about Toot-toot. Even if you decide the PC's aren't getting Lawbreaker feats the wardens obviously aren't thrilled with this approach so you could easily end up with a case where they're trying to take out former friendlies without resorting to the tools that got them into hot water to begin with.

There's also a horror story aspect to "the one that got away" stories in this case. If they don't take out someone they've given bad mental consequences to, especially if the target wasn't the nicest person to begin with, you could end up with some pretty gruesome events happening offscreen (but probably not to anyone the PC's think of as important, not without warning and/or a shot at stopping it). In addition to it's other problems, this is the sort of action that creates arch enemies.

Could be a lot of fun playing in any of these time periods. But if I'm going to add something, I'd have to say it would be intriguing to play in a game set a bit in the future. Couple hundred years from now, standard sci-fi progressions, with orbital industries and enclosed colonies on the moon and Mars. Figure the Nevernever pretty much just follows humans wherever they go but it might make faerie a bit different away from Earth. Also be kind of interesting to see vamps and other nonhumans try to hide in a large enclosed offworld colony.

Two things.

1. I've run several Amber games using the setting based on the novels. I tried talking my players into using the same rules but going with a new setting, but they would never go for it. That setting basically requires that the NPC's from the stories are present, although not necessarily showing up in any scene. The PC's can look them up pretty much at will. I found they were largely archetypal so it was not terribly difficult to portray them. The players who knew the stories were willing to buy into how I ran them and I actually got complimented on doing it well most of the time. I think I largely went with the NPC's having a particular attitude and atmosphere that I tried to portray, one point they wanted to deal with and then let the players direct the conversation afterward.

2. I had it easy in that Amber was setup this way by default but you could readily import this idea into any other game. The powerful NPC's I dealt with were all involved in an intricate and subtle game of chess. Sure the PC's were pawns, but they were also the only pieces on the board that could afford to move. Everyone else was locked because the moment they began to show their real power, the whole board would light up as everyone else responded. In the Dresden Files novels, Harry only looks awesome because he can move around and is largely free to do things. The White Council, the various vampire factions, the Winter and Summer courts, they're all stuck. They can't move. Hell they have a big pact (the Unseelie Accords) that generally spells that out in big letters. You can either add some adversary for Harry & Friends to stalemate against or you can have them join a faction.

Your Nightmares idea makes me think of the Shadows from Wraith (but less animated I think). It can be rewarding if done right but it can also fall a bit flat. You may end up pretty busy keeping track of this and Aspects unless you have a very small group of players or the players themselves help you (as they do in Wraith).

It would definitely be simpler to run if reality shifts were less frequent. Easier to play as well.

I had another thought but it may not mesh with what you're after. It occured to me you could have the effect be localized. Perhaps there's an item of some sort and whoever has it gets one chance to pick realities. Maybe it's very hard to give it up (or get it to leave you alone) even after using it and maybe bad things happen to you as you carry it around.

Differing perceptions can cause problems. I played in a game where that happened awhile back. The GM told presented me with a character who I ended up taking under my wing and protecting. The NPC was actually better than me in combat but clueless about a lot of things, so needed someone to look after him. To another player he presented the same NPC as a monster who must be killed without giving it a chance to think or react. So all of a sudden I have a person I'm protecting becoming the target of an assassination by another PC.

Long story short: It didn't work out well and pretty much broke the game.

This may be an extreme example but I think you'd still see differing views adding stress to the game, especially if they're both "real" to the people involved.

Remember "Summer" does not automatically mean "Good". A character like this may well have to contend with the urge to solve almost any social problem by just pumping anyone around them who isn't overtly happy full of joy. And while it's a strong emotion, it doesn't necessarily make everything else go away.

For example, where you're thinking morale boost, the other character may have fears about the situation which could be dealt with by retreating from it. So you juice them up and you can readily end up with a situation where they're thinking "My friends are being hurt, nothing's quite going right and the bad guy is some hideous monster but I'M SO HAPPY!" Not good for long term mental stability.

Couple ideas popped into my head while reading this.

- Why only have the high-end organization? If these guys are nobles give them their peasants, pawns, serfs in the form of the less evolved organizations like the backwoods lynch mob.
- Do you want there to be any ambiguity about these guys at all or are they pure evil? If you want a sympathetic angle I'd go for them forming initially as a victim's club of sorts, a place for nobility who have been abused/manipulated by fae or wizards or vampires for example. You could add occasional incidents later on to crank up the sympathy value or leave it off for a sort of "You were right once, but now you're just as much a problem as they are." The latter option plays more easily into the hypocrisy element but
- In the real world these sorts of groups are NOT victims. They are ignorant thugs. May be a good idea to consider how the rest of your group will approach the topic and make sure they're comfortable with it.