Don't add entities in data-final-fixes. Other mods can't read those without declaring your mod as dependency.
Instead make your other mods optional dependencies and add entities like normal entities.

@Optera: i just got a crash with the message "unknown virtual signal name: LTN-elec-battle-loco-3" in your LogisticTrainNetwork mod, which is probably caused by this problem. thus I'm reporting it here.

it would be too bad if i can't use both mods (and several other train mods) at the same time, unless every mod author adjusts their mods for each single current and future additional train mod.