Weekly cleaning like when you weed the garden should keep the smell under control.
And you should be able to clos your run in fairly easy.
And you should be able to clos your run in fairly easy.

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I would build your coop to the left of the porch, attached to the porch, and use under the porch as a covered run. A rooster and 3-4 hens will not need a ton of space. Just remember, though, if you build it small to accommodate a small # of birds, then you won't be able to let "chicken math" take over. You will be limited to a small # of birds....
I think if you build the coop under the porch, you are going to have issues with rain water seeping into it. It won't be fun... A little rain seeping into the run isn't as big of a deal.
Using the porch in some way will save you a ton of construction effort and time, so I think you should incorporate it somehow.