I like your ideas. My 30-year-old home had no cleanouts anywhere. When I remodeled a bathroom, I added a cleanout, but there was no practical way to put it in an accessible place, so it's now underneath a 12x12 porcelain tile, marked with a tiny brass plaque that says "In case of poop, break tile." Based on past history, I doubt we'll ever have to do that. I'm also pretty sure it's not per Code.