Others have made a full node w rasp pi, you need a large memory cart. Also the read/ write speed can be an issue from what i read but i never did it myself
Memory can be increased by using swap but it would just cause extra load on the SDcard and it isn't as fast as the on-board memory. I/O speeds isn't a huge issue after going through initial synchronization. Read and write speeds isn't as important as potential bottlenecks in your internet.
Most of people will not install the full node when the block size increased.
Considering the hard disk price is getting cheaper, that isn't much of an excuse. Most modern computers could easily have 1TB of HDD since they are fairly cheap. However, the network would need more high speed diversed nodes than low uptime nodes.