It sounds to me like you are dissapointed in how God has made and arranged things and you feel you could do better. Perhaps you could make a perfect world where no one gets sick and no one dies. No one would steal lie or get angry etc. You would have a perfect world. You would then have done a much better job than what God has done right?
Perhaps the child who experiences these physical shortcomings is blessed in other ways that are not obvious to you. Mentally retarded people often bless those around them in many wonderful ways. I have found in my life that I often don't accurately perceive situations and they appear to be one thing but then I find out they were actually something else. I think you may be seeing the limbs missing as the all in all when in fact there are other issues at work you are not seeing. Often times our sufferings humble us in a way that draws us closer to God. I hope you too will experience that closeness and love with God one day soon.