You can write the code yourself or submit a general idea about it. Let the community discuss and see if anyone picked your idea. In the worst scenario, there might be a fork or a split.
I believe security is always on their mind. No developer is stupid enough to ignore it. I'll ignore the 51% part, but just remember, just because you have the power to do it, doesn't mean you can ignore the cost to do it.
Good point. It all depends on community consensus than anything else. If the BTC community approves checkpoints and other security mechanisms, I don't a reason why developers wouldn't care more or less about it. Security and decentralization has always been Bitcoin's "motto". I'm sure that developers, miners, and community members will work together in order to make Bitcoin the strongest Blockchain in the world. It's already the most secure Blockchain in the world, but there's still room for improvement.
As you've said earlier, anyone can write code or submit a general idea about it. There are many Bitcoin Improvement Proposals out there which are subject to the approval of the Bitcoin community. I believe that something as important as transaction finality should gather the attention of everyone in the BTC space once 51% attacks become a threat to the Blockchain. Considering that Chinese miners still control more than 51% of BTC's hashrate, anything could happen in the future. But knowing that malicious attackers would quickly lose their incentive/reward from the Blockchain, it's very unlikely such situation will happen by then.
It's not that devs "don't care", it's that checkpoints turn it into a game of pot luck, creating disparity. If 'user A' received their transaction before the checkpoint, their transaction is safe, but if 'user B' received a transaction after the most recent checkpoint, they could still lose their funds, destroying any faith they had that the blockchain is impartial, neutral or fair - all things we generally claim it to be.
Or in reverse, users sending payments might profit illicitly if it was rolled back to a checkpoint and they got their BTC returned after using it to purchase a product or service. How pissed off would you be if you were the merchant providing that service?
So, if Bitcoin's security ever fails, it fails for everyone equally. No two-tier lottery where some users win while others lose.
Worse still, game-theory seems to indicate that, understanding the above concept, it could conceivably create additional incentive to attempt a hashrate attack in order to game a checkpoint system.
In that case, Bitcoin should remain as it is right now. Adding complex features or improvements would only make matters worse, in my own opinion. Besides, there are other ways to maintain the integrity of BTC transactions without the need for checkpoints. If 51% attacks become a real threat to the Blockchain, developers could easily switch to a new PoW algo that's ASIC-Resistant. Or they could simply adopt alternative mining protocols like Betterhash or Stratum V2 in order to make mining more decentralized. Considering that Bitcoin's transaction history has remained intact since inception (AFAIK), I doubt the immutability of the Blockchain would be much of a concern in the future. Still, we should be prepared for any adverse situations that may happen in crypto land. It's in developer's best interests to maintain the BTC blockchain as secure and resilient as possible, in order to fulfil Satoshi's vision of a censorship-resistant and decentralized economy for the whole world to enjoy. Just my thoughts
