The most important thing when dealing with bumblefoot is to remember it is a result of uncleanliness and the buildup of bacteria, it has nothing to do with the texture of what the chin is standing on.
I am sorry but I disagree - basic biomechanics are involved in bumblefoot development as well as trauma and secondary infection. Ulceration is primarily caused by the build up of fluid under the callus as a result of an inflammatory response. That inflammatory response is usually as a direct result of unrelieved pressure.
Wire mesh can cause abnormal pressure points which produces thick callus over time - that callus cracks and the cycle of ulceration and infection begins. It is a bit like us walking with a fold in the lining of our shoe - if we walk on it enough it can cause blistering, callus, pain, and ultimately ulceration.
There is a good article on the development of bumblefoot on the ratguide.com site
here. Whilst it is aimed primarily at rats the same applies to chinchillas.
Rabbits can also exhibit bumblefoot - the cause is primarily unrelieved pressure and is, again, attributed mainly to wire (
Merck Veterinary Manual).
Callouses naturally occur on chin feet.
Yes, callus formation is the body's natural response to pressure. It is the excess and/or unrelieved pressure which causes problems - callus formation is (in some ways) a flawed response. One of the first rules of wound management is to prevent pressure being exerted on a wound - the wound will not heal under constant pressure. The only way to relieve the pressure on a chinchilla's feet is to provide softer flooring. In humans we can use a rocker bottomed sole shoe, a scotch cast, specialist footwear, crutches, wheelchair, or (in some cases) total bed rest. Unfortunately we cannot do that with chinnies so we have to provide the next best thing - a clean, soft(isH) flooring and good hygiene practices.
There is also a balance to be struck between allowing the callus to continue forming and cracking and softening the skin a little so that it moves with the gait of the animal but does not compromise the protective qualities of the plantar skin.