I'm in more of a wait and see mentality with this decision.
On one hand this could streamline FTB modded play and create a pleasant experience and on the other, the playerbase will become frustrated that their favorite mod combo of choice can't be utilized and try their hand at custom packs.
This could also potentially fracture the FTB SMP community further as no one server lives long enough to establish on one pack as there is even now a wide wide selection of modpacks the admins will rapidly flitter to and from. Of course this is not a FTB problem, the admins will have to adapt if they really want a community and not a bunch of stooges who they let play on their server for as long as their interest persists in the game.
Also making your own modpack isn't hard, I'll grant you it's work, unpleasant work but once you wrap your head around the pitfalls and have your "I'm dumb, that's what I did wrong" moments you have gotten through the hardest parts; the learning.
All it takes is time, a hell of a lot of patience and at least a brown belt in Googlefu.
Actually it's permissions that are the hard part, that is is you feel beholden to the modders code of ethics and don't go Technic on them then it's not really a problem (until someone goes explosive bees on your pack...).
So you can make your own pack it's not simple but not hard either, but this could only exacerbates the SMP fracturing.
That being said it's most likely that RF based mods will be sufficient in keeping peoples interest and the SMP community will gravitate to the best all round standard pack overall strengthening. After all a lot of the mods that are allegedly being left out saw a usage drop ages ago.