First I want to say that I won’t be able to develop this solution myself, so if the community likes it, other people will have to step up to help carry it forward.
I think Ergo is very solid overall, yet perhaps one of the biggest potential threats is a 51% attack. In order to avoid a 51% attack, it would help if Ergo could maintain a minimum amount of network hashrate. It would not completely remove the possibility, but it would decrease it. Perhaps Ergo should be changed so that the transaction fees increase if the network hashrate gets below an IMNH (incentivized minimum network hashrate). The increase in the fee would be paid to miners. Ideas on what number the IMNH should be and how it can self adjust over time are welcome. It should be set to something that is above the desired minimum so as to leave a protective buffer after the incentives kick in.
Transaction fees would remain as they are now when the network hashrate remains at or above the IMNH, which it should most of the time. This will allow the transaction fees to be as low as possible for the users. As soon as the hashrate is below the IMNH, transaction fees would increase a little. They would keep increasing the longer the hashrate remains below the IMNH.
Users will prefer the lowest possible transaction fees, but they also benefit from the increased security that results from any increase in fees they have to pay due to the IMNH.
Basing the increase in fees on the hashrate rather than the coin price, mining difficulty, or the profitability of mining seems like the right approach. Ergo does not need to support an infinite number of miners, and each miner has different profitability requirements based on differing circumstances. But if the network hashrate gets too low, this would be bad for everyone, as it greatly decreases the financial cost a bad actor would incur in order to attempt a 51% attack.
Even if the incentives work in maintaining a minimum network hashrate, it is still possible to perform a 51% attack. We don’t know how much of the hashrate is controlled by a single miner, farm, or pool. But I will leave that to be addressed in other ways if necessary, perhaps by rewarding all loyal miners such as is being discussed elsewhere. I don’t think there is an accurate and simple way to only incentivize decentralized hashrate that can be incorporated into this idea, or if there is, it can wait until a future proposal/change. I think the scope of this idea is about where it should be should it eventually become a proposal.