What about going down the containerisation route (Docker)?
- Decent PC with lots of cores and memory
- Provision each container to have adequate resources for running game client and bot client
- Probably need some additional automation and tweaking for setting things up but you could run many bots on one decent machine
If you made an investment and had something like:
- CPU: Threadripper 2990WX (32 core / 64 threads) (not sure if there was an issue with virtualization with Threadripper CPUs)
- RAM: 64GB+
You probably would be able to run 20-30 bots at once on one machine.
Just a thought someone will probably poke holes in the idea