Yeah, that could be a problem. Even modern trains often now have multiple locomotives (including in the middle of train sets) to deal with range/weight, so who knows. There’s no reason hybrid trains can’t have multiple locomotives or battery bank-cars for those situations.

As I mentioned above, the freight lines are very conservative with new tech and amortize equipment over decades (often to the point where many rail cars are unsafe, especially outdated tank cars), so even if it exists we won’t see it in practice for awhile yet.