To my knowledge there's no video editor which is able to import DNG sequences in a usable way. Your best option for what you want is to convert the .RAW files to Cineform RAW (
http://www.magiclantern.fm/forum/index.php?topic=5479.0 ). You will have real-time playback and a lot of grading flexibility (not as much as with After Effects route, though).
I don't understand the need for pre-grading raw (preview while editing?) but I do something like that with my current RAW workflow.
I import the frames into lightroom (all of them). I recover the highlights all the way down and some of the shadows, I up a notch whites and blacks to make sure nothing is being clipped and I export them as TIFF sequences in 16bits that I can import into DaVinci Resolve. I batch process all the TIFF sequences to small 720p proxy files and I edit them in Premiere (
). I do roundtrip to Resolve again and do the final grading. I still have some problems reconnecting the footage because of the file naming.
That way you are editing the TIFF-proxys which already have shadows and highlights "recovered" and should have a "proper" white balance for preview purposes. It a really slow workflow and requires tons of disk space but you can do it overnight. I've found it's the one which gives the best image quality to my eye (despite the flickering issue, which is not that noticeable in most sequences in my case
http://www.magiclantern.fm/forum/index.php?topic=5710.0 ).
