We have three options as far as route alignments go.

Spoke and Wheel System On Devoted 2.0 I essentially declared my nation the center of the world and built all ice road routes outward from there. This was great because if funneled a ton of the traffic back to me, and whenever I wanted to trade with people they had to go through "the hub" of the system anyway. Unfortunately, I think we're too far from the center of the map to be the center of a global system to be the hub, which leads me to suggestion two:

Spokes and Wheels System Rather than one hub we can declare maybe 3 hubs along the x axis and have them connect via rail to surrounding areas. Those three hubs can be connected by a high speed, no stops, route running directly along z0. This would place more of an immediate focus on local development and different areas would be responsible for their own development more than in a central system. It also makes short trips easier than a central system.

The Spiderweb Just connect everything when it needs corrected, always with an end to end, no stops, direct line. It'll be a mess, and there will be a lot of duplication, but we can offer to build routes to connect nations if the city owners pay us at least enough iron to lay the rails and diamond and xp to repair our picks.

The Grid Run east west lines on the latitudes and north south lines on the longitudes. Don't worry about connecting directly to the cities, but rather picking a z or x coordinate that gets you closest to the largest number of cities. Cities can build a short shuttle from inside the city down to the trunk line (main through line), perhaps where it crosses other lines. This system will require more transfers to successfully navigate, but it'll be easy to build, and it'll let us cover more of the world with less effort than the other options.

Personally, I'm an advocate of the Spokes and Wheels System. I think we should start with a line at 0z running east west across the world. Simultaneously we should connect all of our towns and other stuff in the area so we can be the first corner of the world with a nice comprehensive rail system.