Here is an example pic I found on web. There are several ways it can be done though. Going with something like that, you’ll want a carbon filter in each room if scent is an issue. If it’s not that big of deal, you could probably at least forgo the veg area. Also, you’ll definitely want dampers on each secondary off the main header. That will allow you to fine tune the air flow. Due to the nature of something like that, i’d make sure you have a decent sized high quality fan with a proper speed controller as well. You may have to run a little larger than square footage calls for to compensate for losses with ductwork, bends, and filters. @Countryboyjvd1971 can probably help with that when you’re ready. It’s my understanding he has some stuff going on, but I’m sure he’ll drop by when he has a chance.
One thing that does concern me, is drying area doesn’t have its own room. Not that it necessarily needs one, but this is the stage that usually requires the most accurate environmental control. So you may want to consider at least doing the same to keep it individual as well.
I like the new layout much better! You could easily flower with 600 hid and veg with 400 here. If and when you’re ready to expand, just take flowering area into the walkway. If you decide to go with led I can definitely recommend a few for those areas. But they’ll be a little more expensive than hid options.