Regarding that service orchestrator, even before seeing Airplane et al, I've wanted to take my Terraform + Nomad + Temporal + Ops experience (coupled with all the other diverse HPC + UX stuff on my GitHub) and make a nice OSS PaaS out of it.
But I didn't because Nomad is "Business Source Licensed" -- so once I put all that work in and try to make it customer-supported, HashiCorp could shut down any commercial hopes once they finally decide to put Nomad on HCP (why not yet OMG?!). But I get why it's licensed like that, no shade on HashiCorp, any of the big clouds could otherwise host Nomad and crush them.
I much prefer Nomad to K8S for what I do (HPC on-prem + cloud-edge). And HCP itself runs on Temporal!