I would be very upset if they put Karin in S/mileage. I'm not really digging current S/mileage and I'd like Karin to be put someplace where I could fully enjoy her. MM, please.
How does what group she is in change your enjoyment of her?
If anything being in Morning Musume means less spotlight for her since she has no charisma or personality. She's just cute but then Morning Musume already has plenty of cute already.
If I don't care for most of the recent S/mileage songs, costumes, choreography, or most of the other members, then I'd be putting myself through torture just to watch Karin. I'd rather Karin be in a group that I actively want to follow. Furthermore, I like Karin and Riho together.
As much as I love Riho, I'd have to disagree with that. Karin is a really good dancer - not as good as Riho, but really good - and she's a much better singer.