A really workable discussion on reusables requires a lot more than one thread. I've worked on this for almost thirty years. Our earliest concepts in the late 1970s were based on Phil Bono's work, using aerospike technology and VTOVL. There's still a lot to be said for that, but the real tradeoffs are much more complex.

As you point out in your post, every aspect of launch system design, when trading reusability over expendability, alters other parts of the equation. I could do pages on the Shuttle alone. Often, things like costs of development weigh in. The perfect reusable vehicle would be one where, like an airliner, fuel costs would be the prime factor in operation. In real life, for orbital space vehicles, designing and building something like this is not completely impossible, but it's definitely a bitch and a half.

Without going into too much detail on how we arrived at the conclusions, some options that have balanced out nicely for us include:

-- Heavy boosters with reusable engine pods that reenter ballistically, and disposable tankage. Good for systems using expensive, pump-fed engines.

-- Expendables with small, reusable manned vehicles that enter orbit. I have worked on both ballistic (technically, lifting bodies like Apollo) and winged designs. This works best with simple launch systems, including some pressure-fed air-launched designs.

-- Air launched systems, similar to the Rutan concept, have big benefits for oribital vehicles as well. A high-altitude airplane is the ultimate reusable first stage. It doesn't deliver a lot of velocity, but it takes you up to where your upper stage's rocket engines can really pick up that high-altitude ISP. I've done a lot of work on this lately.

Getting your avionics back in one piece turns out to be almost as big a cost saver as getting your engines back. And the black boxes can almost always be stuck in the reusable part.

I have noticed that it has been a long time since I worked on a design that was reusable from the ground up as a single stage.