These are some specific parts that I think would improve our options in spaceplane (and normal plane) designs - Mk-1, Mk-2, and Mk-3 fuselage parts that are a quarter and half lengths of what we have now - Mk-2 and Mk-3 fuselage parts that have the standard mix of Liquid fuel and Oxidizer (and all the adapters with fuel) - A Mk-3 to Mk-1 adapter (either with fuel or without) -The avionics package with an actual function. Basically this part should have an aircraft related function that the new SAS doesn't. I suggest the ability to pin it to a point on the NavBall, rather than whatever reference frame the standard SAS uses. This way we might, for example, pin it to the horizon so that the aircraft doesn't nose-up as it moves across the globe as it will with the current system. Of course, this should be separately toggelable (either action group, context menu, or as a separate key) , as needs might change when, say, your SSTO reaches orbit.