It would be pretty cool to have a permission for Forge Essentials like the "fe.protection.use.immersiverailroading.item_rolling_stock.*" so that Players which don't have the Permission can't use Locomotives and/or Wagons.

We want to make a Roleplay Server (GIRC) and we don't want normal Members ("Citizens") to use Locomotives.

Could you be more specific about what permission you think could be useful here?
Like "control locomotive", "board stock", "place stock" etc. ?