Outdoor Cat Play Enclosure Design

The design of my cat's outdoor enclosure allows him to play freely in my back yard. I have a very large back yard that opens onto a 120 acre farm. My cat "Prangles" loves to stalk wild animals and birds, climb trees, explore and live life to the full. We often go on walks together through nature and I really enjoy watching him hunting or climbing. Cats, like dogs, are digitigrades: they walk directly on their toes. Because of this they are capable of walking very precisely, placing each hind paw directly in the print of the corresponding forepaw, allowing them to minimize noise while walking or stalking and hunting. Cats are so dexterous and agile. For example when a cat falls it reflexively twist its body and right itself so that it lands on its feet. It always rights itself in the same way, provided it has the time to do so during a fall. Obviously this doesn't happen 100 out of 100 and you should always be sure that if you live in a tall building or have a multi-storied house to put bars on the windows to ensure that your cat doesn't fall out. Sometimes my cat takes off for days at a time but I think that this is just due to the fact that he is a tom and out looking for lady friends. Sometimes when he comes back I have to take him to the veterinarian because he has scratches or bite injuries from the fights he got into. I have thought of having him neutered to avoid this problem but haven't yet made up my mind. The other alternative would be to design his outdoor enclosure so that he can't wander around but I really don't want to rob him of his ability to enjoy the beautiful nature we have so readily available.