There is now a safe road from dian's island retreat all the way to therother's portal and through to spawn and TC's base via the nether. I haven't reached every portal. I stopped entering random portals after being murdered in a skeleton dungeon. I think there were Wither skeletons in there. Regardless, I made it 3*3 to accommodate any future railroads and sprint-jumping. It's ugly, but it's direct and completely safe from ghasts and lava. Sorry by the way, I bogarted about 10-15 stacks of cobble from therother to finish it. As far as I know, the complete list of Nether-linked locations includes:

dian's place
therother's place
spawn
Owen's mesa
Gondor_is_Lost's place
TinCow/Scienter's base

Missing anything?