I like the idea of using the boosters as heavy lifters. I don't know if the external fuel tank is strong enough to support the payload shown in the diagram (it's a tank, not a column). The genius behind the space shuttle was that 3 of the 4 principal components are completely reusable. Only the external tank is wasted.
We need to move away from the vertical launch method of sending people to space. We need to look into designing a purely passenger vehicle that can be towed to a high altitude, released, and rocketed to the space station. This builds on the successful lauch method used by Chuck Yeager and also the Ansari X winners. Heavy cargo can still be vertically lauched by a Saturn V with the assistance of the reusable boosters currently used by the space shuttle.
The various versions of Atlas missiles were a very thin tank kept rigid by pressurization. The later models, with added upper stages, carried some fairly impressive payloads.
It would be if the components were actually reusable. It is probably more appropriate to say they are refurbishable.
First of all, dropping expensive aerospace hardware into the ocean is not conducive to reusability. The SRBs need a lot of work to get them back into shape.
Next, the space shuttle main engine needs insanely high chamber pressures to generate the thrust required at the pad and provide the necessary throttleability. That drives its operations cost right out of the realm of reasonable reuseability.
Then there is the reentry profile/thermal protection system. Sure it is reusability, but it is so labor intensive that you would be better off using ablatives.
Shuttle reusability is an example of losing sight of your goal. The goal isn't reusability for the sake of reusability. Reusability has to pay for itself. The real goal you are trying to reach with reusability is reduced operations costs. NASA implemented reusable systems that were more expensive than the expendable systems they were intended to replace, blindly assuming that because they were reusable they would magically be cheaper.
Now they are retreating headlong from reusability, having "proven" that it doesn't work. They have proven anything except that enough bad management can sour even the best ideas.
Almost no system on the shuttle is actually useful moving forward, because almost every one was developed with scant attention paid to how much it would cost to maintain and operate it.