Ah, what a lovely plan!
I've begun thinking in that direction before, but back then my closet, my pots, and my knowledge were too small haha
I think that will work out very well!
By allowing composting to take place directly on the soil, I suspect you will be getting more out of it than composting on the side and then adding that. Because there will still be more unprocessed organic matter left, from which the plants can pull complex building blocks and directly integrate them into their plant structures = tapping in to the cycle of
living matter, in addition to the usual culturing of microorgasmic multitudes
haha
I think the tricky part will be not to have that half-compost-mix get too hot.
I can imagine premixing components that add up to a nice C:N ratio so there will be no hot spots in the compost (that in turn could then be frying the roots, or creating temporary pockets of acid, anaerobic-leaning conditions, all stuff we don't want to happen in any big way in there). So yeah, the "heavy composting" would have to be done before if very hot ingedients are to be added.
But hey, that's as simple as throwing the mix in a bucket, getting it perfect humidity-wise, and leaving it for a few days on the side just in case?
Actually, I've already begun doing that for my wormbin, since I noticed it heating up (and the worms getting pissy) after adding a few cannaleaves on top of a feeding. Sheez, it wasn't even that many! So now I mix them and similar stuff under my cardboard/woodchip/leaf bedding before adding them in.
Also, I think that with this nice wormbedding-amendment-mulch layer in place, you could still add fresh materials (N? enzymes? hormones?...) if they're chopped up small.
Herwig Pommeresche (the Norwegian guy who has very successfully been implementing the prinicple of the cycling of living matter for decades) mainly "soilifies" veggie scraps & garden waste in volume while there's nothing growing in the soil. So in autumn after harvest, he brings out large amounts of these scraps onto his garden beds, which get covered with thick mulch. By springtime, they have been digested. Then he plants.
Whilst the crops are growing, he only gives them those protoplasma smoothies (just kitchen scraps/garden wastes blended with water) once a week, poured straight onto the soil/mulch (on indoor plants, he even filters out the plant matter and only gives them the juice, and I
think that's fungus gnat prevention right there).
So what I see going on there, that may be useful for keeping the "integrated wormfarm no-tills" balanced, is the physical size of fresh plant matter additions as a factor in keeping a balance whilst still amending.
I totally hear you regarding the fungus gnats.
As opposed to fruit flies which are manageable, it seems where there's decomposing stuff, we will have them inevitably.
I think that in the end we need to follow nature's principles there too, by expanding the ecosystem to include more competitive eaters and (gnat) predators. Which you can experiment with if you have a room
Oh and possibly, companion plants. A nice border of
drosera capensis, anyone? Your rosemary, I think it was?, sat as
plants in there...
I've seen all sorts of crazy insects in grow rooms, sadly back then I was so busy getting my stuff going I didn't pay attention to the what and why of them. Also, I get the feeling that to get a truly self-sustaining system, just adding this or that single bug isn't going to do it, we need to add a whole network of "who eats who's" and "who helps whom's" to get a stable, self-regulating system...
And that's where I find it gets daunting.
When I observe my garden outside, there are many critters that wander through it whilst foraging... flying, crawling, and burrowing insects, birds!, mice, hedgehogs... and all of them do their part in managing the garden, possibly contributing indirectly towards pest management. A closed space like a grow room won't allow for "migratory" foragers like that.
So that's where IMO the most experimental part will be: to build a concsiously reductionistic, artifical ecosystem that nevertheless includes all the organisms needed directly and indirectly to keep the fungus gnats in check.
FUN STUFF!!!!!