PS - About that oxidizer...
N2O itself definitely has scaling issues. When plumbing lines get larger in diameter, water hammer is sufficient to detonate it. That is, the channel diameter is sufficient to propagate a blast wave. N2O is a monopropellant by itself. That adds additional safety concerns. Hobby size plumbing doesn't really have that issue.
Other good oxidizers such as H2O2, LOX, etc, have their own handling concerns - cryogenic, corrosive, hypergolic with lots of organics, etc.
Solids are just simpler to handle once they are cured, and are a very mature technology. In the large scale end of things, as soon as one goes to a liquid oxidizer for ISP improvement with all the associated handling and logistics, one might as well go fully liquid. The fuel is usually easier to deal with than the oxidizer.
I's in the small to intermediate size range where hybrids may make the most sense commercially (say roughly, O through S range, and of course down to a fair bit smaller for hobbyists). But there isn't much of a market for intermediate size rockets at the moment, non-military, though I could be mistaken. The cost to hitch a payload ride on a larger rocket has decreased a lot in the last few years.
Gerald