I wonder if there is anyone here who works on CloudFoundry or OpenShift and could comment on this, or comment on the proposed capabilities of Flynn (https://github.com/flynn/flynn-spec) compared to the capabilities of their systems.
They actually don't use LXC though and implement resource control with Cgroups. That said, Cloud Foundry is extremely difficult to get setup and running in my experience (even with the v2.0 recently released). It sounds like one big differentiating factor is that Flynn would have fewer moving pieces (Cloud Foundry is at least: BOSH, Warden, VCAP?, CF itself, etc.).
CF is actually very plugable as well - there is a well defined internal API, which you could just add components that listens/publishes to - however, I don't think its encouraged, neither have I seen a single example of it.