I like the idea of adaptive blocksizes.
I also favor the idea that capacity should always outpace demand, so I think the increases have to be substantially greater than this. I think Ethereum does it in a smart way. If I am correct, it is something like 20% more than a moving average of actual capacity used. This ensures blocks keep getting bigger as needed.
How do you differentiate real demand from spam demand?
If someone like Ver decides to dump millions of dollars worth of spam transactions in order to make the blockchain huge, how do you stop this? since if it's automated, the blockchain will just adapt to this demand (even if its fake) centralizing the nodes as a result.
I just don't see how flexible blocksize schemes aren't exploitable.