Indeed I like very much the proposal, because unlike BU it creates very clean and easy to follow rules for block size. There is only one little problem. The ridiculous downsize to 300kB at the start. What I would propose is to let blockstream to develop the code and then at the very end just change the initial size and blocksize increase factor to some reasonable values on which the majority of miners and users would agree. Maybe 2MB and 30{88c91daedd271a990a10650c05d769cae2765e0603edf30ca95f18704e5748e8} yearly increase? What do you think?