What kind of storage capacity and download speed do BCH full nodes need in order for BCH to successfully operate as money for the world?

It has been claimed that visa processes 1,700 transactions per second on average, so this number will serve as the goalpost for this analysis.

BTC, processing 1MB blocks every 10 minutes, is claimed to be able to process roughly 4.7 transactions per second.

If a 1MB block is being processed every 10 minutes, then it adds about 144MB to the chain each day, or 53GB each year. This amount of space can be easily accommodated by the storage technology of today. So how does the space requirement scale in relation to the amount of transactions per second?

BCH currently has a block size of 32MB, and though they are not always filled to the brim as BTC blocks are, we will assume that each block meets the maximum capacity of 32MB. The chain, under these circumstances, will consume roughly 4GB of space per day and 1.6TB of space per year. This should provide about 150.4 transactions per second on average.

So what does the block size need to be in order to successfully accomodate 1,700 transactions per second? Assuming the 4.7 transactions per second when processing a 1MB block every 10 minutes, we would need about 362MB blocks in order for this to become a reality. If that were the case then each day would require about 51GB of space, and 18TB each year. This can run for anywhere between $350-$860 per year (for a 20TB HDD) which isn't unreasonable. It won't prevent miners from being able to run their operations, and dedicated members of the community could still easily run a full node.

According to AT&T Cable copper wires currently have speeds of 20-38 MB/S, while fiber technology offers 45+ MB/S. A network with 362MB blocks every 10 minutes would only need to download around 0.6 MB/S

Australian researchers on May 22, 2020 have achieved an internet speed of 44.2 terabits per second.

The hardware capacity to handle 1,700 transactions per second already exists and is affordable. As time moves on and Moore's law continues to hold true, there will eventually be a point at which the cost of necessary storage space vastly decreases while human population only moderately increases.

In the future the cost to hold the entire blockchain will be decreasing faster than the growth of the blockchain, the growth of the blockchain being limited by the growth in human population which can never keep up with technological innovation. Eventually it will cost a few dollars to hold the entire blockchain and the price will still be trending toward zero.

Outlook for big block BCH: Highly sustainable