That implies a fork of the kernel, nothing less. Rationale:
If you read carefully the problems with cgroup are with exposing implementation details and therefore locking the current implementation in its place, along with some misdesigned features that utilize current implementation details in way that appears to be both difficult to maintain and nonsensical to end users.
If "dgroups" remain in kernel tree, then the current implementation is still locked in place unless emulation of old interface can occur. I doubt it can. If dgroups remain out of kernel, then the "dgroups patch" likely won't apply cleanly and can't be made to apply cleanly few minor releases down the line.