Just because a homeworld is Darkness owned does not mean it would be safe. Whenever combat is released you would still be able to attack people on a homeworld owned by Darkness since by that time A/E will be a thing of the past and you would not need privilages for attacking others, at least that is what I assume.
By making a homeworld Darkness owned it is essentially making it so that factions and players cannot gain control of the planet. Meaning no building their own facilities or anything else that the faction/player would need control of a planet to do. So, no shielding or secure bases would be possible on a homeworld that is Darkness owned though I would assume you could use one as a temporary waypoint.
Another point, when spawning a player can only spawn on their homeworld unless they join a faction first though we all know that there are many new players that do not join a faction first which leaves spawning on their homeworld.
Overall, a Darkness owned homeworld is not safe as anyone could easily kill a player on such a homeworld just as easily as any other planet. In my opinion a Darkness owned homeworld would make sense as Darkness would essentially represent a specific races sovereignty over their own homeworld.