PSA: if someone has a full >50% hashrate for your cryptocurrency, there is NO NUMBER of blocks where confirmation is safe. Once you get beyond 50%, you can reverse an unlimited number of blocks!
(What happened to BGold, CAN be done to BCH or maybe Bitcoin if Bitmain wants to...)
You assume he cares (governments and hackers compromising someone else's hardware don't) and doesn't have more to gain by compromising it (eg, shorting the target or promoting an altcoin).
Bitcoin's security model was never meant to be "trust a single entity because X, Y, Z".
So is there anything regular Joes ilke myself with my home laptop can do to help make network secure without relying on Bitmain being the 'with great power comes great responsibility' hero (not villain) or is it a bit too late for that and assumption was somewhat naive/flawed?
Not with just a computer. You can buy miners from non-Bitmain (eg, @canaanio and/or @HalongMining) and/or support a PoW change to Bitcoin (but this requires consensus from the entire economy). Ideally, buy mining hardware that comes *prepared* for such a PoW change...
1/ The ASICs need to be made with a switch to do a SHA2 variant in addition to normal SHA2. The manufacturer would keep the details of their variant secret until consensus is reached for a PoW change.
2/ At that time, all the non-malicious manufacturers (ie, sold widely) release information on their variant, and we make the new PoW algorithm be (for example) "either CanaanSHA2 OR HalongSHA2 OR ...".
No, I'm saying Bitmain has more hashrate themselves than everything they or anyone else has ever sold.