What were those other choices/what transition plan did they have? v6 does have a transition plan, and as far as I can tell it's not really possible to do any b

What were those other choices/what transition plan did they have? v6 does have a transition plan, and as far as I can tell it's not really possible to do any better than it's already doing. v6 is as interoperable with v4 as is possible to be, given the design of v4. Can you explain how it could have been better? What transition plan would meet your requirements?