Sizing help

[aart]

I'm thinking ply its walls and as you suggest run roosts down its entire 2.5m length. Not sure how that works with the current sliding door/tray/nesting boxes though

You'd remove the coop wall that faces the run.
This might work to support roost end near nests.
https://www.backyardchickens.com/th...ng-in-nest-boxes.1134399/page-2#post-17749535

 

[M Brennen]

It looks very nice. If you haven’t thought about it already, I would just make sure you have it secure so nothing digs underneath.

 

[rosemarythyme]

Not sure how that works with the current sliding door/tray/nesting boxes though ☹

You scrap those. Rip out the floor and the inside wall. Nests could possibly be moved and reattached, or replaced. Make the mini coop/run into one single bigger coop.