no way is any miner ever going to support this.
You do, of course, realize that if one lonely cpu starts mining upon this chain, you will have been proven utterly wrong?
Not to mention the amount of botnets that will hop onto this bandwagon.
Oh wait - self-contradiction in one neat paragraph - quite an achievement!
an implementation of BitPay's adaptive block size algorithm, adjusting in the range 2MB-4MB
Unsafe without Segwit,
Well, no. Segwit does absolutely nothing to make larger blocks safe. Although other changes bundled into The SegWit Omnibus Changeset do. Which of course are available for other implementations to adopt, should they so desire.