Hello,
the problem with AVC-Intra is the same as it was with DVCPro50:
They are superb codecs for (camera-)recording from uncompressed,
but are not robust enough for high-end post production.
(robust = significantly keeping quality at re-encoding)
They are perhaps the best native camera codecs for DNG, but nothing for DI.
That said, one of the most popular DI codecs before Apple released ProRes,
was DVCPro50 ...
But the more I think about the problem, the more I like DIRAC PRO aka Schroedinger ...
http://diracvideo.org/
It's open source!
Best regards,
Bernhard