If you can get a shed and modify it, it would likely give you better results than modifying this little coop/run. However you can still keep this and use it to brood chicks outdoors, which would let you jumpstart the whole integration part and allow you to add chicks earlier.I love this idea!
The other day, I was looking at it thinking “wouldn’t it be nice if the whole thing was the enclosed coop”.
My other option is to buy a shed and replace the coop but if I can modify it, that would be better. The coop does come apart into two separate sections.
It would be a little different than the one you linked, since the roofline is not the same height from the box to the run.
Thank you so much for commenting because this gives me some serious things to think about and I might be able to get it done in time to get chicks this year.
I turned part of my old prefab into my outdoor brooder, and the chicks start interacting with adults as early as 10-14 days: https://www.backyardchickens.com/articles/short-on-time-recycle-a-prefab-brooder.73985/