Today's my day to argue with you, KM.
Everyone gets their day.
Although it looks like WotC and I were on the same wavelength before!
Just think of it as a bonus "power" you pick up at 5th level, but it couldn't be phrased that way because the classes in 4E use the same progression in terms of level-based abilities.
That's what makes it seem sloppy to me. Square peg, round hole. If it doesn't work, why would you try and force it in? Just do something that works with the layout. Especially if the reason you'd be forcing that weirdness isn't that important.
And I don't think making all "rages" daily powers is a "weird design choice" at all. It makes perfect sense, and I think it adds nice flavor to the class to have their signature ability and their daily abilities be the same thing.
What if they had some sort of "basic rage" as a feature? Something that maybe just turns on the additional at-will power benefits and maybe gives you a little damage or temporary HP kicker, maybe even something you can only activate when you're bloodied (or something that activates automatically when you get bloodied or when you use your second wind).
This would mean that the rages could still be mostly attack dailies, while still giving you some advantage for Rage Strike at 1st level.
Alternately, ditch the idea of the rages replacing each other and just let a Barbarian "turn on" one or the other as a free action each turn. Thus, no need for a Rage Strike style feature. Or design them so that they interact without being too powerful. There's not that many of daily attack powers, after all, it's not an insurmountable task to compare them and use them all at once.
It makes some sense, but if it's going to cause problems like this, is it really worth it?
The basic idea is that it's ugly to have this ability sitting there, useless for four levels. That's not a functional concern, but it is an annoyance, and it doesn't need to exist. It makes it seem like the Barbarian is a 5-30 class, not a 1-30 class. It's dead weight on the character sheet for four levels.
It's not a bad idea, but it looks bad. It's sloppy. Ugly. An obvious bandage over the wound when there is no pressing reason, I think, for the wound in the first place. It cures the symptom, not the disease. It's probably like another metaphor that I could conjure up.
