oh stuff speaking of fuel you could latch on some detachable engines and just burn fuel from the craft itself
once you have it in orbit, pop off the engines and have a tanker dock and refuel
whenever a spaceplane needs a Δv boost, i spend a handicapped amount of time assembling a high-orbit relay station around kerbin and/or the target planet, and when those stations need refuels i set up mining rigs on low mass moons with tankers that fly up the refined fuel using a mule drone
3-5 missions' worth of effort to permanently reduce required effort elsewhere- if every large planet gets an orbital gas station, ships with efficient engines can basically do whatever they want for as long as they want
