“They need to use EM rails up a mountainside to achieve launch velocity without all the extra weight of fuel and tanks.”
Seems like a good idea. Also they could use an air-breathing, winged vehicle to get up aways in the atmosphere and get some initial velocity.
Exactly, overcoming the initial zero inertia is the biggest expenditure of energy. Doing so without having to carry the fuel and containers would vastly increase their weight limit.