Both upsides were already easily solvable. Most distro's rc scripts already call a function to start a daemon. That could easily have called a helper program to set up the cgroup and register on dbus to act as a controller for the group.
Meanwhile, at least Debian's rc scripts already had dependencies listed in their headers that could be used to compute a start order. It could as easily be used to compute a makefile to start in parallel.
The problem is, now that the init process will be such a hairball of dependencies, it becomes harder to implement such solutions without seemingly unrelated bits breaking. For example, no reasonable person expects the GUI desktop to break if you switch out init. (and no reasonable person creates such a dependency)