I fully support this proposal and hope we can move forward with a real BIP and an actual implementation based on it.
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.
In this proposal, it would take
years of continuous spamming to achieve a dangerous block size. Not only mempool spamming (like now), the transactions would have to be actually included in the blocks, so it would be a very costly operation.
You can do the math: the increase of the base block size would be a maximum of 250 kB per year (that is the important number regarding to the quadratic hashing problem), while the total block size only could change 1 MB/year.
What I like regarding the last proposal (5% per period) is the non-exponential approach to block size increases. So if the block size becomes bigger it still is equally difficult to "spam the blocksize to the moon".