@Machaca
All potential causes are addressed in the updated system. Of course it should fly ETOPS - the 787 has twice the electrical redundancies of a 767: four engine generators vs two, two APU generators vs 1.
I would not read redundancy into having the engine and APU generators in pairs at each of the three locations. Rather, I would identify reasons for the smaller generators, having nothing to do with redundancy.
1. At 250 kva each at the chosen voltage (230 volts 3-phase), the amperage per phase at the main engines is already over 600 amperes in each unit. It has got already to be difficult to build a unit this size for 400/800 cycle service.
2. Starting an engine can apparently be accomplished by one of the two generator/starter on the engine. This materially reduces the problem of throwing this machine, in starter mode, across the line. Should the main turbine be having a bad day, the second generator/starter can be added after the first is turning; that is very much easier as being geared to the turbine, it's already turning also. It is initially putting current into a non-moving electric machine that is a real problem. The diesel engines that drive the ramp generators just do not have any short-term higher power output, in contrast to the short-time needs of starting rotating electrical machines. It's a common cause of diesel engine-generator stalling.
3. The 250 (or 225 @APU) KVA generator/starter size has a potential market in lesser planes, which is an economic factor.
4. Loss of a main turbine takes out two generators. How realistic is it to call one generator a back up to the other? The APU generators are the back up, hence the importance of being able to start that system aloft.
5. The 787 electric power load is double or more its predecessors. Double the number of generators is more necessary than redundant.
I would not assume those who raise questions here necessarily fail to understand these types of systems.
OE