As far as removing dew claws from and adult that hasn't had any problems. I probably wouldn't, but then again I'm a penny pincher that would rather use that money else where. Now if the dog was already going under and it wasn't that much more expensive I might. If I was a rescue and had an application that was perfect in every other way and that might be the deal breaker to him/her finding a good home and the potential adopters where willing to pay the extra, then yes I would probably have it done.
After reading some of the requirements on different rescues(not talking local pounds) then I would probably give the OK with a prepaid neuter at a later date. MOST people that do the jumping through hoops to get a rescue dog are above average homes anyway.. The slightly below average homes end up not going through a rescue because they are not going to be approved anyway. They end up answering ads in the paper, craigslist, various other ads or going to the local pound where if you have the money you can pick and take your dog home in the same day.