- Replicas: could be made with YAML templating

- Update/rollback policies other than stop-first, very useful on a local machine?

- Resource limits: stayed in v2 to sell Swarm, although there's cgroup_parent which has to be created manually

For example, Swarm supports `configs`, while Compose does not - and I use `configs`, and would much rather not have to have separate service definitions for dev and prod to work around such insufficiencies.