Pleased to see how sensible you are being over the welfare of your hens Max. The manufacturers don't care about hen welfare, they only care about the money they can make by selling these fairly cheap coops, knowing that someone like you, will be buying another one to accommodate the hens that you realise are overcrowded! LOL
My partner built me lots of henhouses and coops over the years we had our chooks, one of them was a 6x4ft shed, which he then cut the side out of to accommodate the 10 hole rollaway nest boxes I bought, but for your hens you would be fine with 2-3 nestboxes inside. Brian then made the perch so it went all down one side of the shed, but was removable so I could clean out easily and check for redmites.
Being a shed, it was so much easier for me to get inside for egg collecting and cleaning out. I'll see if I can find a pic of the inside, but not sure if I've got one that shows the perch, I was more interested in my nestboxes which I was very proud off. Rollaways are good, as it stops the eggs from being pooed on!
I was right, it doesn't show the perch on the right hand side! xx
After this photo was taken, we were given another same sized shed and Brian added it to the rear of this one so it ended up 12ft long! The hens loved it in the winter if it was too wet outside!