A few other points based on what you've written:
Look into black soldier fly bins. Easy to make. You can throw entrails and bits you're not using in there and generate free protein. Assuming NZ has a good natural BSF population to draw in. I also like them because they are a non-biting and their pheromones or whatever, scare off biting flies (I have seen this season's biting flies go way down so I feel like I can speak on this firsthand. Hadn't done a damn thing for the mosquitos.)
Also, ducks have done way more for bug control. If you see opportunities for muscovies, they don't put on weight as fast as Pekin, but their meat supposedly tastes like roast beef. And while their incubation rate is for shite, if you can get them established, they brood really well and increase numbers fast.
In terms of chickens-- unless you want to sell pure breeds, I feel like mixed breed is the way to go, especially if you're in a more isolated genetic pocket.
The reason why you're not seeing people trying to rotate in small amounts of new chickens a week or month or whatever comes down to a few things:
1. Spring hatching tends to have stronger offspring. I have been hatching into summer and definitely saw a dip in incubation rate and early survival. If you have grow lights, that can help.
2. You don't want lockdown eggs with still incubating eggs. And hatching eggs can knock around eggs still incubating. Having multiple incubators can help because you can put lockdown eggs in one and have that rolling incubation you are talking about.
3. A bigger issue is that chicks need extra time and attention. Especially to catch coccidiosis which, for me, seems to hit between 1-4 weeks. If you're rolling chicks out, you'd probably be better off with medicated feed. But even then, failure to thrive, or introducing to the flock, etc.
In the beginning of the season, we had 4 hatches and a shipment and raised everyone up together despite there being maybe a six week age difference. You have to be more aware of smothering, or of tall chicks just clomping around on top of little chicks-- not to be mean but there's a height disparity. The upside to raising multiple hatch ages together is that raising bantams up with larger chickens hasn't been an issue. They're just part of the flock. The downside can be it is harder to see what doesn't fit: like coccidiosis behavior outside of reddish poop.
But early chicks are exhausting and some people just aren't into it (I like incubating and the first 3 days or so. After that, I start to be more interested in them at 6-8 weeks.) you might have a different take and really love chicks.
You're going to have so many instances of "I would have done this differently," but a lot of that can be individual to your situation. Having your coop and garden setup before chicken math hits you though, and having predator protections set up with game cameras, live traps, air rifles or BB guns if you are allowed-- that's pretty general stuff.
Another thing (and maybe I mentioned some of this before) is that having multiple breeds or breed mixes will surprise you. I was really looking forward to Bresse and have found them kind of lackluster for me. I was expecting to not like Hamburgs but the female is now my favorite. Same with the mottled java but for a different reason.
My F1 mixes (or mixes in general since I got them from someone else's flock so can't say 100% the parents were pure bred) have had the lowest death rate. We lost one to coccidiosis early on (symptoms were subtle at first and no reddish poop) but other breeds lost several.
I've greatly enjoyed my Brahma mixes but have found white feathered feet breeds are a no because their legs look awful.
My Orpingtons are fine, sociable. Cuddly. But they're not my favorites.
My red leghorns are a bane. And they were supposed to be the friendliest of my leghorns. But good God, I've been trading them off or culling.
I hated my polish at first because they were such drama queens. But now they've settled down a lot and are pretty cool to have around.
Anyway, long story short: there are good reasons to have solo breed flocks, but based on what you've told me (and especially because we are raising meat birds we do have the benefit of not having to worry as much about, say, a decade long breeding plan for flock improvement-- you can start over from scratch every season if you want) I don't think a solo breed fits your goals/needs.
The near part about starting out in the beginning is (and I assume it's this way where you are as well) is that poultry people are legion. But sometimes hard to find. Once you start networking, you'll have opportunities for rehomed poultry, even if they know you are likely going to cull for meat. And being open to the various breeds and even species, it's pretty cool who has what, what they're breeding/trading/selling. And they can give you and indication for what works in your area and what doesn't. Though I wouldn't try to breed/sell what they are doing because you don't want to step on toes (unless it is a really rare breed where more birds is better for everyone.)
Thanks again for such great info and for the time you took to provide it.
I've looked into BSFL and mealworm farms. Mealworms are out - they take too long to reach anything of maturity, require too much hands on work for my liking, and require that I purchase regular inputs for them. We're rural, I do predator control, and NZ has a problem with Australian Brushtail Possums and feral goats, so feeding BSFL is a non-issue.
That said, I couldn't actually figure out what the nutritional benefit was of BSFL vs. just tossing them a plucked possum carcass (plucked because brushtail possum fur is tied with arctic fox for second warmest fur in the world, it's absolutely luxurious and if I don't do anything with the fur myself I can sell it). I'd love to understand if there is a nutritional benefit...? Or is it just that it seems less gross to feed chooks insects instead of animals? I'd love any insight into this.
One downside I've seen though is that BSFL can make eggs taste muddy. Doesn't seem everyone has this experience, but it is well enough documented that it seems to be a thing - I think it happens once they become greater than a certain percentage of diet.
I intend to increase my trapping to offset some of the cost of our chooks - especially if we go the path everyone here seems to be suggesting to do our meat rearing in a compact period of time. I've read a handful of threads on this and understand that people get way in their feelings about it, but I'm absolutely feeding my chickens animals I kill and fresh roadkill when I come across it - I have no reason to believe that isn't a natural part of their diet. Plus the dog will be thrilled to eat anything the chooks don't want/can't get to fast enough. We also have neighbours that have volunteered to collect their food scraps and a locally owned store 20 minutes away collects all their produce that's passed its prime to give to anyone who wants it.
We should absolutely look into muscovies, that said I'm a little hard on ducks at the moment. A couple of years ago we had some 3 English Grey x Sebastapol geese and 3 Cayuga ducks. The geese were amazing. We'd have them again, for sure. The ducks were great, but the drake was a bully. He quite early asserted his dominance over all the birds and, when the geese hatched out goslings, he proceeded to kill a number of them. The rest were killed by the geese being poor first time mothers (and us being poor first time goose owners) so we lost several to being squashed in the nest. The ducks ended up going into the freezer, and the geese took themselves off to greener pastures at some point while we were overseas on holiday. I do understand that was one drake, of a different breed, and I shouldn't paint them all with the same brush.
I'm also in a place of wanting to want quail without really wanting them at the moment - they just seem, convenient. But I'll revisit that after we get good and settled in with our chooks. I'd want to build something relatively large for them and we've got too many other things going on right now.
Thankfully, we don't really have the kinds of predators you guys have over there. 9/10 dogs out in our rural area will be caged when they're not working sheep or cows, we don't have raccoons, we do have a number of things that will eat eggs and chicks, but, besides stoats and occasional feral cats we probably don't have anything that would be bolshy enough to go after a chicken in their coop. But I do have hardware cloth, understand animal behaviour well enough to be a proficient trapper, have a slug gun and intend to get a crossbow.
You're right about whether or not I care about having a single-breed flock. I just simply do not. It was circumstances that caused it more than anything else, and I'll probably get another batch of the same eggs from the same guy to do a second hatch this year. Then, when we cull back to a few to carry us over winter, we'll reassess and fine tune from there unless something quite obvious strikes us in the meantime.
I don't do social media anymore. That said, we do still have regular livestock shows around the region and that's where I'd go to meet chicken people I think.
Also, thanks heaps for taking time to explain the sense behind not having a rolling flock. Reading your reasons makes tota sense, but without any prior experience in animal husbandry it's not as obvious as it might would be to others.
Thanks again!