An initial pipeline could be built with a lower target speed. This would postpone some of the potential challenges with regard to heat dissipation, and also route selection.

For example, you wouldn't have to worry so much about tunneling under a mountain to ameliorate the G-forces if you are traveling more slowly. Once you prove out the route (which could still be competitive with any existing train service), you incrementally build tunnels and modify the route to improve your target speed.

(As for heat discharge, Im pretty sure that was addressed in EM's original paper - dumping the excess heat into an on-board water tank which is exchanged at the end of the ride, or are you referring to something else?)