"Or, have the NPS embraced the packraft as a legitimate way to explore the river (without a GC river permit) and adjacent canyons?"
Thankfully the answer is yes. The NPS deserves credit for listening to users and working towards sensible regulations for packrafts.
Currently, when applying for a normal backpacking BC permit you can check the packraft box. Downriver travel is limited to 5 miles total. With portages we just squeaked in under this limit. Reportedly a more complete policy will come out later this year. It will almost certainly mandate wearing an official PFD while packrafting. Hopefully it will expand the floating limits a bit, perhaps using some kind of zone system. Conventional rafters are apparently quite territorial.
Additionally, you can put in for a river permit through the normal lottery system, but arrange to have a launch zone other than Lees Ferry, and a takeout other than Diamond Creek. You have to stay on "schedule" if doing this. For instance, if you wanted to hike Nankoweep down, put in, and float down to hike the North Kaibab out, you'd have to put in on the date when a generic river trip with your launch date would be reaching that area on the river. This might be a good approach for a Little Colorado trip.
I'd like to see the Lees Ferry road torn up, and all the rafters have to hand carry their gear ~2 miles to the put-in. It would be an efficient and democratic way to cut down user-days annually (~500,000 in 2012), oblige trips to have a lighter footprint, and unclog the lottery system.