Hello,
We raise our brolers in the winter due to livestock show. We are still learning having only done this for 4 years now. We live way in the south, and we have learned that heat is not a broilers friend. When it gets into the 80's, they just shut down (after a week or two old).
To answer your question about mess, we have learned that concrete sand from the material yard works best. It keeps everything nice and clean with only a periodic leaf raking of the top. Sand soaks everything right up. I do not know if you can use it for your situation, but it is a blessing. It is also a great help should your waterer overflow for any reason.
Sand also provides them with grit. We generally use a little pine shavings when we first get them to help with warmth, but they are a big mess. We do not use them anymore, and chickens are fine.
One other concern is room or space. You are right, these chickens eat, poop, and sleep. If you want less cleaning, a minimum of 2 sq. feet per chicken should be allowed after 4 weeks old.
We then take it and till it into our garden.
Hope this helps.