The heavy, static, overbuilt recommendation could be a mistake if one switches to N2O instead of O2 for the oxidizer. In the catastrophic situation where the N2O goes monoprop in the tank, having a heavier wall tank may just be equivalent to creating higher pressure before it bursts. Sometimes it's better for some parts of hardware not to be overbuilt. For instance, one wants to design so that a nozzle blows out as the first failure point for a solid propellant motor. That's just an example. Consider the types of failures which might occur, and then design for either eliminating them, or for how those failures shall occur if they cannot be eliminated. A failure that occurs in a controlled fashion is generally preferable to an uncontrolled failure.
If I'm recalling correctly, I remember a story about a solidly overbuilt motor static test where a bulkhead ended up embedded in concrete half a mile away. The motor was large but within the realm of what a dedicated hobbyist could produce. Rocket motors are high power devices. It is something worth keeping in mind.
I do like that "without a nozzle" suggestion though. However it significantly changes the dynamics as the pressure differential through the injectors will be much greater than the nominal 150-200psi for a reasonable burn.
There is actually a great deal of research and information available now on hybrids. Not nearly as much as other forms of rocket propulsion, but enough to spend quite a bit of time absorbing! The fundamental design factors are a bit different for a hybrid than a solid, as the hybrid is halfway towards a full liquid system. It contains elements of both types of systems.
As a quick example, the scaling factor Kn for a solid propellant motor (which many are familiar with; certainly all EXers) which is the ratio of the burning surface area of propellant to the nozzle throat area would be replaced by a different scaling factor which is the ratio of the effective injector surface area to the nozzle throat area. Though, I'm over-simplifying it of course.
If that last paragraph isn't totally obvious to a person, then that person is nowhere near ready to start designing hybrids!
Ultimately, the research tends to leave a person with more ideas and more questions. But they are more practical, more interesting ideas and questions!
Gerald