The most critical in my opinion: Address the 1 MB blocksize limit to allow Bitcoin to scale.
I would fight to keep it at 1MB for the years to come. We need off-chain solutions for that and there are many in the works. Raising the block size would only slow down progress and harm those projects.
AND why?Just 1 thing, for I it would be transaction times, cause waiting for those confirmations is wayy too long sometimes
1minute is just as bad as 10minutes when in a supermarket, especially as this 1minute block time sometimes will also take 20minutes. We need other solutions to that and there are off-chain solutions.
But to answer the OP question:
What? I would add proof of stake.
Why? It's cheaper and better aligned with keeping the fees low and the network secure. With proof of stake there is no reason at all to have fees beyond keeping the blocks free of spam. Those holding bitcoins would have a huge incentive to keep the blockchain rolling even without block rewards and transaction fees. The claim that with proof of stake the rich become richer is based on the assumption that mining is a for profit venture but with mining (securing the transactions) being built back into every full client cause we can, we wouldn't have to worry about the 50%-pools and wouldn't be blamed for wasting energy on mining. Also those mining chip companies could focus on more meaningful stuff.
We could continue to give the block reward to proof of stake blocks and reserve the mining fees to proof of stake, aligned with the block reward halfing. At the next block reward halfing we don't half the block reward but we half the POW blocks, doubling the POW difficulty and adding POS.
