Electric is a game changer for popular aviation. Why? Because aviation has (fortunately) very strict safety standards. So the aviation version of common car engines are vastly more expensive than their car counterparts. They also require expensive maintenance regularly. Electric engines are mostly maintenance-free, and the biggest point is, you can have any number of electrical engines on your aircraft - the common drone has 4 independent engines, and people-carrying crafts can have 10 or more, basically eliminating any reliability related safety concerns.
People put common car engines on aircraft all the time. The problem is that "certified" aircraft engines are expensive due to that designation (think regulatory capture). There are several cheap auto-engine options for homebuilts. Maintenance can be done by the builder for homebuilts too. The costs are almost completely due to the small market size.
I agree with you that electric motors are awesome (they're what I do) and you're right that you can easily put 2-4 of them on a fairly conventional aircraft for amazing redundancy.
The problem with the quad-rotor configuration is that the motors are doing all the work. With real wings you get a better lift to power ratio but you also lose VTOL capability.
Having said all that, I'd still like to see a small short field aircraft automated to the point that the general public could use it.
