I am still working with my contractor to see what can be done to add another return air on the first floor of my home. A few weeks ago we were looking at trying to get something through my very shallow crawl space (I posted a question on that too).
The only alternative to running it through the crawl, which will be difficult and somewhat expensive, is to have it near the kitchen in a mud room/pantry area right off of the kitchen. Virtually all the supply air that will be pulled through this return, except for the supply air in the mud room, will have the return path through the kitchen. I know it is not acceptable to have a return in the kitchen, but what about right outside of it and having the return path through the kitchen?
My current setup has a single return at the back of the house and all the supply air from the front of the house and the mud room has to pass through the kitchen to get to the back of the house (kitchen is in the center of the house). This is the contractors argument stating that the new return really is no different with return air still passing through the kitchen, but this new return would be right next to the kitchen.