I'm not sure I understand your comment. Are you proposing to move all the systemd features in the kernel? Why do you think it would be a good idea.

Note that one of the stated goals for systemd is to make good use of all the new fancy features are already available in the Linux kernel but not many people use because they are not portable (eg. control groups). Also note that some cool features have already been merged in the Linux the kernel after the systemd developers created them (eg. memfd).