I agree that battery cages are a terrible system, BUT:
-intensive feeding is not force feeding. The birds have been bred for an incredible growth potential and have a digestive system to support it. They don't suffer in eating huge amounts.
-battery cage flooring is wire mesh with some sort of tray below to catch the feces. Unless there's a buildup and very poor maintenance, the birds are not sitting in their own feces. Allowing this to happen is not in the best interests of the producer as they will lose money for filthy birds, so it's unlikely to happen.
There's something that needs to be clarified though- broilers are not raised in these cages. Broiler chickens (meat birds) are typically raised in barns, where yes, stocking density is a problem, and yes, sanitation can also be a problem. This is what is considered "intensive husbandry" in terms of meat birds. The housing system you describe in which the birds are kept a few to a cage with limited mobility are only laying birds.
Here are a couple articles for you:
http://www.fao.org/ag/AGAInfo/home/e.../part2/2_5.pdf
http://www.ciwf.org.uk/includes/docu...cages_1991.pdf
There are distinct differences in how laying chickens and meat chickens are kept, each with their own concerns for animal welfare. Battery cages are the system in which laying hens are kept that is being outlawed in the UK. Deep litter is the system of keeping broiler birds (and other bird species such as turkeys), and while improvements need to be made to this system as well, there will never be a switch to keeping broilers free range.