It actually did work like angel ring, it has always allowed creative flight... up until the poing when you took over the development.
If you are porting the mod, try to port all its features.
Because I was really surprised when after spending so much time for making GraviChestplate, it occurred to be just regular jetpack, which was completely useless for me!
If you still don't believe me, you can ask SeNtiMeL or at least check his thread
You can also go on FTBWiki and read about GraviChestPlate.
Check also this video. Ask people on reddit. Anything. But port things right, and do not claim that it hasn't been there, because it has and it was that thing which attracted people. Now it's gone.