This is already seriously impressive, especially for how new it is - but, since this IS Rimworld after all, what're the odds of the mod eventually including more-sophisticated and unusual high-Industrial and Spacer-tech trains, rails, and related shenanigans? A few possibilities that occurred to me off the top of my head:

[only enabled if VFE - Power and/or Rimatomics is installed] High Industrial-tech nuclear-electric rail engine, powered by a miniature internal fission reactor and steam turbine. Steep upfront manufacturing cost, but comparatively low moment-to-moment maintenance due to how long uranium fuel lasts, and can haul a very large/heavy load of railcars.

Some sort of pure-electric locomotive that depends on a new rail type with integrated power feed, requiring at least one tile of the rail network to be in a tile that has power generation infrastructure and has a power conduit feeding into a special power input machine next to the physical position of the rails or somesuch. Probably best suited to use on routes that are going to see a lot of frequent rail travel along them.

Spacer-tech counterpart to the above - an electromagnetic hover-train, which of course requires a new "magnarail" railway type that also needs power like the regular electric rails. Probably way the hell faster than you'll ever practically need, but potentially more useful with certain other mods.