!WARNING!Please restrain from using mod for now. I'm having some nasty bugs I need to resolve before this mod becomes usable at least at its core.
I'd like to present a tiny mod which adds a better alternative to vanilla portals. Actually, these should assist in creating a whole inter-dimensional transport network which uses Nether as a hub.
Short list of features
Entry gateways can be opened from any dimension, not just Overworld
Nether-side gateways (let's call them exits) are opened in a much more predictable way, and in a much lesser range than vanilla portals' bizzare spawn mechanic. This will give you much more control over where you'd like to put them
You can adjust exit location by placing anchor in Nether before opening gateway
The person who opened gateway becomes its owner, and he's the only person who's able to close one via special procedure. Otherwise gateways are completely indestructible. Even nasty beasts like Enderdragon or Wither can do no harm to them. Of course, this doesn't take into account Creative mode. Though if you destroy any part of gateway in creative, it just gracefully closes.
No relinking. Two gateway structures are linked during creation and until removed. So you'll always return to exactly the same place where you came from.
Entities will maintain momentum and direction when travelling. Moreover, exit position is perfectly predictable. Any entity will leave gateway like it has travelled through pillar horizontally in a complete vacuum. So a minecart entering from north will always leave from south.
Minimum travel cooldown - 4 seconds as for now, just to prevent accidental items jumping back and forth indefinitely.
Supports rider-and-mount pairs. So you can sit into minecart on your base in Overworld and get up only in the End. or a distant Overworld quarry, wherever your rails lead.