Do you see yourself down the road when they want to implement something like the last fork using it as a sandbox to test the ramifications of proposed changes?

I don't think so. It's difficult to test so many changes without real, interacting users, but they already improved the testnet in order to be better prepared the next time.

I guess one of the main problems was that there were too many changes at the same time in the last fork (was really a big one) and maybe the time for testing the huge amount of updates was way too short. The next HF's will come more frequently so that the outcome will be way better manageable and predictable.