There has been proposal to change the PoW in case of potential 51% attacks
from malicious miners during a fork. But such a change in PoW renders
multi-billion-dollar of ASIC into worthless. which hurts economy so much
and the average innocent mining users. I would propose, instead of PoW
change, we could change the system to the same double sha256 PoW but mix it
with PoS features. Such a PoW+PoS system has several advantages:
* It protects existing multi-billion dollar investments from innocent
mining users,
* A malicious miner cannot launch attacks and rewrite the blockchain with
51% or even more hashrate,
* If we insert 4 PoS blocks between 2 PoW blocks, we'll have 2-minute block
time span, that solves the long confirmation time problem,
* We'll suddenly have 5 times of block space, that solves the scaling
problem,
* The PoS blocks only mine transaction fees, so the 21M cap remains,
* With careful design, the PoW+PoS transition _might_ be able to deploy
with a soft fork.