Basically, I am wanting my dog to retrieve birds, but also hunt rabbits and foxes. I may also want to use him to smell for blood trails from deer, elk, etc. Would this be possible, or would it just confuse him?
You can't teach an old dog new tricks.
Hunting dogs are trained from pups, you wouldn't necessarily confuse your dog, but you might discover that it doesn't do the best job of what you want it to do (rips your birds apart while retrieving them, isn't fast enough to catch rabbits and foxes, leads you to a steaming pile of poop instead of following a blood trail) Or you might find he isn't that smart, I have a labrador retriever, and he's pretty dumb, he loves to chase things but I've never seen him catch anything. Some cats will let him catch up, but that always results in my dog getting scratched in the face and running away crying (then he goes and pouts to mommy).
One of the reasons we have so many breeds is because certain breeds proved to be more effective than others for certain tasks. Pointers are great for letting you know where animals are hiding and flushing them out. Hounds proved to be excellent trackers and following trails with their extra keen sense of smell. Retrievers proved to be efficient at retrieving game birds without shredding them to bits. Greyhounds were fast enough to chase down and kill rabbits, foxes and coyotes. Irish Wolf Hounds are the reason that wolves are extinct in Ireland. Dachshunds with their powerful bodies and short legs were bred for digging into borrows and hunting badgers. Yorkies, believe it or not, were originally hunting dogs, used to eradicate small mammals like rats, mice, even skunks and other borrowing animals, those little ankle biters are mean for a reason-they're killing machines.
If you already have a dog, you're not going to have much luck training it to be effective at preforming the duties of all the other breeds, but if you started training him early, you could probably teach it how to do an okay job at at least some of them. If there was such a thing as a well-rounded hunting breed, then we'd probably hear about it more often, but as it is hunters prefer their job specific breeds.
According to this site the Pudelpointer is the best all-round hunting dog, so if you want one dog that can do it all, you should consider getting a Pudelpointer pup and start training it from a young age.