The StarGate/Nether portal is in spawn for a reason. Its mostly for the fact that it players could build nether portals, there would be portals all over the nether. Even if each portal built by a player linked to the one portal that's the I.e for the one in spawn, it would be a tedious proccess to have them linked and want not, and players having portals all over the place. Back in 1.8 people could pay 5,000 coins to buy a StarGate in there home, but that was shot very quickly.
I'm just saying, it has been done and it was a tedious process for admins to coordinate a nether portal in you faction home.