However, you might use a space elevator at L1 or L2 (or both) that allow capture of HEO or launch or inter-system vehicles with only efficient high impulse rocket motors.

Note that you could use Spectra/Kevlar or other common high strength materials with a taper ratio of only 4:1 with a lunar elevator. It might take "only" ~50 tons of spectra to hang the weight and allow lifts of a 1000kg or so... its much more doable than earth or mars.

https://en.m.wikipedia.org/wiki/Lunar_space_elevator