I've got a bone saw, but pretty quickly used a set of loppers to cut bones and spines. Until I watched the Outdoor Edge DVD set which showed how to disjoint cervids without cutting the bones, if you figure out how to cut the tendons with your knife you can pull off the forelegs and even skull without getting bone shards or dust anywhere. It can sometimes take a bit, and you might need to touch your knife up afterwards but it's a good skill to develop. Also, a convenient knife sharpener or steel should be part of your butchering kit. I've got one of those cheap ceramic rods things, it works well enough and I can sanitize it in the dishwasher or bleach it or whatever.
ETA: videos on jointing deer without a saw.
Sorry for hijacking. To keep on topic - you don't need a custom knife to do these things. I'd use my skinning or field dressing knife rather than my butchering knives, which are a bit more delicate.