Extra launch pads.
As a fellow KSP player, with over 700 hours playtime, I have always found it annoying how I had to get all the way across to the runway to launch a boat or have to fly to the poles just so I can do a land speed record. It's those minor inconveniences, and yes, I could just get a mod like Hyperedit, but the problem is that I keep having to download updates for it every game update, which I cannot be bothered to do.
It's not I'm the only person to think of this, but it would be helpful to have some more rocket pads, runways, a few ship launches and so fourth actually in the game, or maybe the feature to create a runway at a flagged landing site or something, so that you can take off planes and save planes away without having to fly all the way back to the KSC. It's a bit of a redundant idea, but it would be pretty badass.