Speaking of train fac. What IF we use something else instead of, well, rails, but still commit to same principle with is "units need something underlaying to move/function at all"? And there we we have one option with is... grid!
Just imagine factory units with depend on grid existance (and probably power level as more in depth gimmick). Its just like planes factory, where plane lob, ehm, i mean, player, usually watching over team instead just his front to support offense/defence. Train lobs (aka esteemed players) in turn will be more dedicated to eco side because without grid they cant do anything.
Another possible core featue as was mentioned before - carry defenses while they are active. To counterweight this make every building use energy to work if they dont and triple or quadruple existing energy reqirements for more powerful options. Also bigger structure mean slower speed, just like with hercules carrying bandit or detriment.
To make it feel more like actual train make sure every unit can be attached to other from same factory, possibly providing eachother some benefits like more speed/less energy usage for buildings etc.
Possible units for such factory (btw, make general cost of each unit on the level of tank factory or even more)
*Obviousy locomotive - providing thrust. Maybie speed boost ability like swifts have.
*Gun wagon - wagon with guns only on sides. Increase damage % to every linked wagon, decrease overall speed
*Shieldwagon - wagon with will provide shields for nearby wagons and itself. Cost more then aspis in exchange of more capacity and regen speed (even when under attack?)
*Dronewagon - (there not so much drones in this game, dont you think so?) wagon with up to 10 drones with you can customize like in Future Wars mod. So its possible to go full with guns or shield/repair drones. Providiong more passive regen and speed to every linked wagon.
*Anti air wagon - same with gunwagon, but air
*Link wagon - provide huge grid around itself and slightly increaase basic grid of other wagons.
*Artillery wagon - you know about Big Bertha in real life? Thats it. Decrease overall movement speed.
Feel free to polish this idea and add details, but i doubt someone will make it. Remember modular factory?
