Tracker bug for fixing missing dependency on crontabs with the following changes to FPG as approved here 
Adding Tracking, FutureFeature keywords to avoid rawhide -> f20 rebase of this bug.
I have formally retracted this feature since FPC members are under the assumption that it is fine to introduce a new package or a sub package and have that sub package depend on systemd when neither that nor the original package contained systemd units or otherwise has or had an existing hard dependency on systemd.
In other words they have chosen to introduce an dependency on systemd where there should be none which at that point you could just as well migrate everything from cron to systemd unit which requires a completely different implementation ( thus completely differently constructed section in the guidelines ) and is absolutely not the intention of my proposal since cron is not 1 to 1 replacement for systemd.
Cronie has it's purpose for those components that do not depend on systemd as well as serving administrative and end users cron jobs handler and we should keep it that way since both components ( systemd-timers and cronie ) complement each other.
But since FPC are such experts on how this should be implemented in the distribution it's best to allow them to do just that as well as observer how and what they themselves will actually migrated and leave Red Hat to clean up that mess they will leave behind in RHEL 8 and it will start affecting RHEL customers.