Looking good mate. Dare I ask one little question please...
The roost bars, they are going to go higher than the nest boxes aren't they, only (andHF prob best to advise) I read that its best to make sure the nest boxes are lower than the roost bars as the chooks look roost at the highest point, so if the nest boxes are higher than the bars they tend to want to roost in the boxes.
Really hope my fears are put aside.
For a small house it's not not really practical to arrange the roosts to be significantly above the nestboxes and having the roosts a few 10's of cms above the nestbox entrance wouldn't have a lot of effect. I've had houses where the roosts were slighly above the nestboxes and they still roosted in the nestboxes. I think they find the warmth and security of a small enclosed space to their liking. My current houses have rising roosts but that does'nt seem to encourage them to always use the roosts. It's very house and temperature dependant just where they feel comfortable roosting.
Traditionally in commercial laying sheds the roosts are placed high with dropping trays beneath them and because hens naturally would lay on the ground so the chicks can get in and out, nestboxes are placed low down. Hens don't fetch food for their chicks like wild birds but take them out foraging for food which when they find a tasty beetle they will throw to the chicks. Chicks are pretty independant and mobile from shortly after hatch unlike wild birds chicks.
If you can arrange that the roosts rise up slightly from the entrance that's not a bad arrangement but I wouldn't spoil the design to acheive it. See the design of the Lenham roosts to see the idea.
By the way laying houses aren't intended to be used for hatching in and to do this you need to set up a separate house for a broody to hatch and brood in. These are usually at ground level with open fronts with a grill which allow the chx through but restrains the broody.
HF