I'm not sure this would work. The G and B stars orbit each other and each have their own planets. That works as long as the planets are much closer to each other than they are to the other star. Next, there are circumbinary gas giants. This is reasonable as long as the gas giants' orbits are much larger than the mutual orbit of the G star and B star.
To have an O star orbiting in this system, its orbit would again have to be much bigger than the orbit of the circumbinary gas giants, otherwise those planets' orbits would not be stable. Finally, to have a circumtrinary comet belt, those comets' orbits would again have be much larger than the mutual orbit of the O + G/B stars.
I think this is all possible as long as the system is very very big. The trick is, every time I say an orbit is "much larger" than another, think 10 times wider. 788
In your setup there are 5 levels of hierarchy: 1) G star planets, 2) G star - B star, 3) G+B star - gas giants, 4) O star - GB+gas giant, 5) comet belt around everything else. That means your system spans a factor of about 10^5 = 100,000 in size scales. If you add in the fact that there are multiple planets per system, which must be spread far-enough out to be stable, you're probably at about a factor of 1,000,000.
In the local parts of our Galaxy, a system can't be larger than about 100,000 AU without getting torn apart by the Galactic gravitational field ("galactic tides" is the technical term). In the denser environments where stars form, that limit is somewhere between 100 and 10,000 AU depending on the environment. Where O stars form it's more like 100-1000 AU since those form in denser star-forming clouds.
Your system is basically at the optimistic (local Galaxy) limit and implausible in the more constraining (star-forming region) limit. If your smallest orbit is 0.1 AU then your largest one is 100,000 AU.
I would recommend reducing the number of levels you have (where you have to make orbits bigger) and packing the levels you have with more planets/asteroids/comets. For example, here is a system with 8 stars but only three levels of hierarchy:
And you can substitute one of the levels of stellar binarity for planets:
Those images are from a very packed system I created a few months ago: https://planetplanet.net/2016/04/13/building-the-ultimate-solar-system-part-6-multiple-star-systems/
Here is another example with one planet and 5 Suns: https://planetplanet.net/2016/03/22/an-earth-with-five-suns-in-the-sky/ 788