Another idea. When it comes to collecting resources outside of your reach limit, there could be a special operations building that produces "extraction teams." With this building, you could sent your team out to gather resources. This would have to be heavily regulated though, maybe make it so you can only do it once every 24 hours, and only when located at the base. Other buildings you could add are vehicle depots, airports, and naval stations (If located near water.) These buildings would allow faster movement of troops between areas as well as help with firepower and defense. When one of these buildings is complete you can upgrade your extraction team to use a vehicle to grab resources, each vehicle from your depots allowing for different speeds, distances, and terrain. Again, only allowing this to happen once a day. The extraction team could also be moved to different lands (movement times needed) and maybe allow one team for every lvl. 100 land.