Initial code. Does not work properly.

UNLICENSE

@@ -0,0 +1,24 @@
+This is free and unencumbered software released into the public domain.
+
+Anyone is free to copy, modify, publish, use, compile, sell, or
+distribute this software, either in source code form or as a compiled
+binary, for any purpose, commercial or non-commercial, and by any
+means.
+
+In jurisdictions that recognize copyright laws, the author or authors
+of this software dedicate any and all copyright interest in the
+software to the public domain. We make this dedication for the benefit
+of the public at large and to the detriment of our heirs and
+successors. We intend this dedication to be an overt act of
+relinquishment in perpetuity of all present and future rights to this
+software under copyright law.
+
+THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND,
+EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF
+MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT.
+IN NO EVENT SHALL THE AUTHORS BE LIABLE FOR ANY CLAIM, DAMAGES OR
+OTHER LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE,
+ARISING FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR
+OTHER DEALINGS IN THE SOFTWARE.
+
+For more information, please refer to <http://unlicense.org/>

control.lua

@@ -0,0 +1,82 @@
+-- If only you could rotate locomotives that where connected this mod would be so much easier.
+
+local movingstate = {
+	[defines.train_state.on_the_path] = true,
+	[defines.train_state.path_lost] = true,
+	[defines.train_state.no_schedule] = false,
+	[defines.train_state.no_path] = false,
+	[defines.train_state.arrive_signal] = true,
+	[defines.train_state.wait_signal] = false,
+	[defines.train_state.arrive_station] = true,
+	[defines.train_state.wait_station] = false,
+	[defines.train_state.manual_control_stop] = false,
+	[defines.train_state.manual_control] = false,
+}
+
+local function rotate(loco)
+	loco.disconnect_rolling_stock(defines.rail_direction.back)
+	loco.disconnect_rolling_stock(defines.rail_direction.front)
+	local ret = loco.rotate()
+	loco.connect_rolling_stock(defines.rail_direction.back)
+	loco.connect_rolling_stock(defines.rail_direction.front)
+	return ret
+end
+
+script.on_init(function()
+	global.movingstate = global.movingstate or {}
+	global.lastmode = global.lastmode or {}
+end)
+
+script.on_event(defines.events.on_train_created, function (event)
+	global.movingstate = global.movingstate or {}
+	global.lastmode = global.lastmode or {}
+	if event.old_train_id_1 then -- We can ignore the second one since the first old id is the one that gets its stuff copied.
+		-- Train changed
+		global.movingstate[event.train.id] = global.movingstate[event.old_train_id_1]
+		global.movingstate[event.old_train_id_1] = nil
+		global.lastmode[event.train.id] = global.lastmode[event.old_train_id_1]
+		global.lastmode[event.old_train_id_1] = nil
+		--@todo: current schedule id too?
+	else
+		-- Train created
+		global.movingstate[event.train.id] = false
+		global.lastmode[event.train.id] = true
+	end
+end)
+
+script.on_event(defines.events.on_train_changed_state, function(event)
+	local train = event.train
+	if train.state == defines.train_state.manual_control or train.state == defines.train_state.manual_control_stop then
+		return
+	end
+	if event.old_state == defines.train_state.manual_control or event.old_state == defines.train_state.manual_control_stop then
+		return
+	end
+	if movingstate[train.state] ~= global.movingstate[train.id] then
+		global.movingstate[train.id] = movingstate[train.state]
+		global.lastmode[train.id] = train.manual_mode
+		if movingstate[train.state] then
+			for _, loco in pairs(train.locomotives.back_movers) do
+				global[loco.unit_number] = rotate(loco)
+				train = loco.train
+			end
+			train.manual_mode = global.lastmode[train.id]
+		else
+			for _, loco in pairs(train.locomotives.back_movers) do
+				if global[loco.unit_number] then
+					rotate(loco)
+					global[loco.unit_number] = nil
+					train = loco.train
+				end
+			end
+			for _, loco in pairs(train.locomotives.front_movers) do
+				if global[loco.unit_number] then
+					rotate(loco)
+					global[loco.unit_number] = nil
+					train = loco.train
+				end
+			end
+			train.manual_mode = global.lastmode[train.id]
+		end
+	end
+end)

info.json

@@ -0,0 +1,11 @@
+{
+  "name": "Noxys_Multidirectional_Trains",
+  "version": "0.0.1",
+  "factorio_version": "0.16",
+  "title": "Noxys Multidirectional Trains",
+  "author": "Noxy",
+  "contact": "donotcontactme@example.com",
+  "homepage": "https://mods.factorio.com/",
+  "description": "Sneakily rotate locomotives that are being pulled backwards so that they actually help with acceleration instead of just being dead weight.",
+  "dependencies": ["base >= 0.16.0"]
+}