Sounds like a good plan - I hope that some BYCers with more imagination will chip in, but from a practical, rather than aesthetic point of view here's a couple of things I would consider.
1. Are there other windows in the shed / playhouse that can be opened for ventilation? - opening the windows directly onto the coop / run may give you issues of odour / dust.
2. I'd lower the height of the wall to give the chickens more daylight and you will be able to see them more readily from the house.
3. if you go with suggestion 2 then you may have sufficient bricks to recycle for the "coop" part of the construction which may improve the aesthetics.
4. Take a look at the roofing over the run area as from the photo it seems its creating a "V" with the shed / playhouse and ensure that there is effective guttering in place (don't want the bedding / coop flooring to get wet).
Thats all i can think of (its only just gone 7am here in Nairobi so my brain is not what it could be ).
Ok, and maybe consider using something like clear corrugated plastic for the wind / rain protection? - it will provide a little more light inside the coop area.