A 10 Gbps network is MUCH slower than even the smallest oldest PCIe slot you have. So cramming the GPUs in any old slot that’ll fit is a much better option than distributing it over multiple PCs.

Technically it’s empty space that’s being wasted, if you fill it up it’s being useful!

If it’s more permanent show them an Azeron Cyro at https://www.azeron.eu/ It’s a mouse with a thumbstick, you can play almost any PC game with one hand. Comes in both right and left handed versions.