Don't know your specs, but what you need are 'touring' shoes. They're usually the only ones you can walk around in and not have the cleat hit the floor. I found a pair of Cannondales a few years ago and coupled w/'thin' spd cleats I've got the clearance I need for doing on/off the bike type errands. Any of the big name cycling gear companies, Lake, Specialized, Shimano, Diadora, Northwave, etc. all make a touring shoe that should work.

Taking a regular pair of 'sport' shoes and carving slots in the soles for the cleats?...I dunno...it could be done, I suppose. Maybe, go to an 'old school' shoemaker w/your idea and see if it's possible. Those guys are really good at what they do...you may create a 'niche' market product.