Looks like you're more caught up with the facts than I am. But I don't know, management is still management, even if they're made of better stuff than Mr. Kim. Taking T-ara into the fold would mean a lot of things. First and foremost, dealing with a "rebel" idol group. Like you said, the last thing the agencies want is to have rebellious idols, and if T-ara succeed in breaking from CCM, they will carry that legacy around with them. I'm pretty sure some agency heads have it in their minds that they don't want to bring that kind of element in to influence their younger talents. I mean, SM actually asked Sooyoung to stop doing that yelling impersonation thing, so there's obviously some disconnect between the mentality of the management and of the fans. Also, it seems widely recognized that up to four members of T-ara have various struggles with performing on stage - bringing T-ara into the fold would mean accepting an idol group with those shortcomings who nevertheless broke from their parent company. And the new company would need a good vision for the future of T-ara - just a matter of having the right stylistic vision and creativity to accommodate them, but still, they'd need to have the right people to make it happen. To a certain extent, Mr. Kim worked around T-ara's shortcomings because he had to, lacking as wide a talent pool as more successful agencies.
I remember the Shinhwa thing, but I think they were a bigger deal back then (than T-ara now), and more consistent across the board. I don't know much about DBSK, but Big Bang, all five of those guys look pretty solid. And I'm a little confused about how exactly the Kara thing played out. But who knows? Mr. Kim may have been a dolt for going public with saying that rebel groups should be blacklisted (that did happen, right?), but that could be a de facto policy among the agencies.
Nevertheless, I believe the best thing for the members would be to break from CCM, don't get me wrong. I hate to see anyone being cowed by a bully, let alone these seven. And in spite of the above I'm sure they can make something work - they just need (to continue) to work hard and find an agency with a vision that suits them.
But yeah, the wick on the powder keg's been lit, and the clock is ticking. I hope the girls understand the kind of fight they've got on their hands, and have the will to fight it - and, like, get quality legal assistance. I don't know how much they've considered their options, as far as breaking from CCM and what everything would mean, and how far they're willing to go for their own sake. I think Soyeon is sharp enough, and strong enough, but she'd need all the members with her - and there's still a chance I overestimate her mettle. Hyomin is a bit sheepish but I think she could be counted on for support if she were adequately inspired. I hear Eunjung is heavily influenced by her mother, and I can't speak as to the quality and quantity of that influence, but from what I've seen she's not as strong morally as she is physically. Boram and Qri are old enough to know what's what, but I don't know much about them, and Jiyeon and Hwayoung are hardworking but young; bottom line, they need to stick together and stand up for themselves. LIke you said, there's no way they will accept (or endure) conditions at CCM in the long run, but the gauntlet's been thrown and they need to answer. Especially for themselves, but also for labor relations in K-pop and for all the fans - the young people with their own dreams and hearts and whatever who want to see the good guys come through as winners, who would be especially disheartened to see a bad situation drag on.