Earlier quoted context omitted.
Why not? RedHat will let you run arbitrary binaries just fine on OpenShift - both long-running/worker/"PaaS" and on-demand/per-request/"FaaS". Obviously this is tightly locked down with cgroups.
How would you modify systemd unit files for each user of your public cloud? How would you manage the sockets once you have more users than sockets on a server?
As for having more users than sockets, is that really likely, considering there are 64000 available ports?