Borg–at least as it is published in those papers()–and these other schedulers are really design to maximize the availability of large distributed apps.

() The real Borg now does a lot more...

But there is a completely different world if you look elsewhere. In batch systems like supercomputers (HPC), you want to maximize throughput, not availability. It is common to have something closer to your design: a inventory of jobs and scheduler that allocates workers to them. E.g. https://hpc-wiki.info/hpc/Scheduling_Basics