I think the loader redux mod had to add quite a bit of code to support trains, unless I'm not remembering the right code base. Possibly that's also why miniloaders wrapped an inserter instead...
Anyway, I think this isn't something we can just turn on from the logicarts side.
Note that researching inserter bonus techs speeds up the carts built-in loaders. There was a recent bug fix for this, where carts would fail to auto-load until the first relevant tech was researched.
