You know what... That would be really nice... I never thought of that. Ryo and Yuu... I am so totally going to draw some pictures for them... Anyone got any suggestions of their group name? 4Yuu? (Ryo's birthdate, 15th; 5-1=4 and Yuu's pun in his name)
Since it's my current imas obsession... The only thing I've found of the two of them is a video on NicoNico where they're dancing to Panda Hero. Wait...
Here it is. As for the name, it's too complicated a pun...? Akizuki(秋月) and Kisaragi(如月) both share the "月" kanji, which apparently can mean "Month" or "Moon." So a reference to either one...? (Like with how they named Ryuuguu Komachi, what with the Sea-related kanji.) I personally will root for "New Moon" or "Lunatic."
Either way, Yakusoku should be Yuu's image song, lyrics having been written by Chihaya. And his image color is Gold. Or something else that looks good with both his blue hair and Ryo's green color.On that topic, I don't think we know Yuu's age, but Chihaya was 8-ish when Yuu got in the accident, if I remember correctly. Yuu was a bit younger than her, so 6-7-ish? So his age in 2nd Vision (AKA the current state of things) would be 14-15ish, so about Ryo's age or a year younger.
I understand what you mean when you say that there's no reason for change in Miki & Haruka's personality. However, I also agree with you on the point that Miki could be awakened Miki in that AU... 
Yeah, there isn't much of a reason for the change, HOWEVER! A change in just Chihaya's personality wouldn't make for an interesting AU.
So Awakened Miki and Depressed!Haruka...? No wait, Dark Haruka. Definitely Dark...