Genetically Modified Human Embryo

I am a strong believer of the use of genetically modified human embryos. There are numerous people in my family that have diabetes, and I feel a potential cure may be found using this method. I know it is extremely controversial, but I also see first hand what it is like to live with a devastating disease. What concerns me is finding a cure, and this in turn, will improve the lives of future generations. I would love to hear an opposing view arguing my point.

Stem cells, by all means grow and use them for cells/etc.  Complete human clones (although I think they are inevitable), I'm not sure about.  For one thing, for all you religious folks out there (I'm not one), where does its "soul" come from?  Are "souls" available on the supermarket shelves?  What would a clone be like without its "soul"? Do you make a deal with "God" to sell/give you a set quota of "souls", one to a customer?

Is a clone property (of the person who made it, or who commissioned it? ) Is it sentient; would it feel the need to sacrifice itself for the "common good"? If not, does that mean its brain is defective?  Then, are other parts of its body possibly also defective?  If it is not sentient, and it's not useful for body parts, what good is it?

I think there's a whole hell of a lot to think about before we go down that slippery slope.