the quality of the idea isn't the problem - it seems fine to me, but it's outside my expertise - the issue is the difficulty of the change.
you would have to get people like bitmain and canaan and EVERY OTHER miner AND user of bitcoin, far more than 51%, closer to 90%, to adopt the new code. and make no mistake, it would, in effect, be a new coin entirely. unless absolutely everyone transacting in BTC upgraded to the new software, the old would remain, and would still function.
there's no way to change bitcoin's POW without forking and creating two bitcoins.
That's certainly true, mate. In Bitcoin's current state, it's hard to achieve consensus across the whole Blockchain. Remember Bitcoin's proposed "SegWit2x" solution for scaling Bitcoin? At first, it was hard to achieve above the required threshold to activate SegWit. But then, consensus was achieved after reaching a common agreement (called the "New York Agreement") in order to scale the Bitcoin blockchain for the world to use. While Bitcoin had the green light for SegWit activation, the "2x" part that was meant to increase the block size to 2 MB simply failed. Imagine changing Bitcoin's PoW algorithm that has been used since it was launched, to a new one. Miners would be reluctant to accept changes to the Blockchain, defeating the whole purpose of decentralizing Bitcoin.
It seems to me that a "soft fork" would be the best way to go than a "hard fork" for the security and stability of the Bitcoin blockchain. But a change in consensus algo, definitely requires the former ("hard fork") to work as intended. In this case, DigiByte is more decentralized than Bitcoin because of its multi-algorithm design for consensus. In the event Bitcoin experiences a 51% attack by Chinese miners, people could resort to other blockchains (like DigiByte) with ease. It's even possible to create a fork from the original Bitcoin blockchain using a multi-algo PoW model for consensus if anyone desires to do so. We've seen how people have parted their own separate ways with "forked" versions of Bitcoin that would satisfy their needs (remember the scaling debate and Bitcoin Cash's inception?).
Nonetheless, time will tell us if Bitcoin will continue to be centralized in the way it's mined or developers come up with a solution for it. Luckily, there's a solution called "BetterHash" which aims to decentralize Bitcoin mining with new hashing protocols (more info here:
https://medium.com/hackernoon/betterhash-decentralizing-bitcoin-mining-with-new-hashing-protocols-291de178e3e0). If this turns out to replace "stratum", then the Bitcoin blockchain would've achieved an advancement within the mainstream world. Adoption of new protocols/solutions are necessary in order to keep Bitcoin as decentralized as possible. Just my opinion