uh, even when I spare the hardware for this, and no way to dedicate myself to it and put it to work. maybe soon

500GB Hard drive for blockchain files seem is enough, right?
500GB HDD only able to store blockchain for 1-2 years. I would suggest 1TB HDD since it's also have far better price efficiency.
but I was thinking something, whether such a node can be used for help with transaction acceleration?
No, unless you mean rebroadcasting transaction (either manually or use script which do it automatically)