I like this proposal. It creates predictable system with feedback with neutral rules. Specific parameters and issues have to be fine-tuned, of course. But it needs both miners and Bicoin users to agree and to actually "act like change is needed".
Like stated elsewhere: Miners decide what is the longest chain. Full nodes decide what is the valid chain. Bitcoin is the longest valid chain. So it needs both. And block size change proposal and mechanism should reflect that.

I have a meta-question... why the details (in the first OP post) are a (dynamic) PHP page?