But seriously, the only way to keep the same level of filtration as that which is achieved with the micron filter is to increase surface area while maintaining the pore size of the filter substrate. IE: a longer or wider micron cartridge.........
Your filtration will only be as good as the size of the largest particles that are allowed to pass through unfiltered. This changes a bit as the filter is in service, because as the filter catches more and more debris, the pore size decreases and you have better filtration, albeit at the cost of reduced flow rate.
Also, all the gunk you find in your filter canister is not only from what has been filtered out of the water, but bacteria and all that grew there as organic material became trapped in the filter medium and fed of this material.
Now, and interesting project would be to daisy chain two hot 250's together, with the first stage utilizing your concept gunner, and the second stage using the micron filter. If your idea is providing the same level of filtration of that of the micron cartridge, it ( the micron cartridge) should almost never become clogged.
I think what you have achieved is the best balance of filtration to service time that works for your situation. I am skeptical that it is doing so while maintaining filtration at the same level in regards to particle size.