Because realistically, you can't just dive straight into bullet train tech

I made it that way primarily because I wanted it to change the way rail networks are designed from the very start. I've contemplated making it into an upgrade, but I need to be sure that this upgrade doesn't require them to completely redesign all of their existing rail networks to accommodate the new trains. Also, I want the upgrade to come fairly early since my intent was for these trains to be used in the main part of the mid-game as part of sprawling rail world style factories.

Well, you can make it a separate mod if you want.

I think that's the best approach, too. I would split it into two mods and make one into an upgrade style mod.

I also want users to be able to use this mod in "memoryless" mode meaning that they can activate it temporarily to debug or test rail networks, then deactivate it easily without restarting. It's harder to offer this in an upgrade-style mod.