Can a factory be self-replicating? Well no, but I think I got pretty close.
Album here: https://imgur.com/a/A1694
3 features that would make this quite a bit easier to grow to truly preposterous sizes:
- Allow ctrl+placing blueprints so they ignore conflicts and just place what they can (same way you can place extractor blueprints outside ore fields).
- A central list of all trains and the ability to control their orders from it. Maybe it could be a mid-late game "control center" building or something.
- Just any sort of load balancing for train stations. Grouping stops as a single "logical" station or special rail block that just instructs trains to pick any of the platforms following it - whatever works.