IMO , i think you are trying to push it too far . Ok DCS is a simulation, but its also a real time application, you can't simulate everything in the same time, sometimes you need to fake some . DCS is great for planes, heli, how missile gun and other react, but implementing a true fragmentation simulation would really put processor on their knees(just like cbu are atm ^^), unless its simplified .
I think the best way to combine it, is to create this famous splash zone , as said, depending on your distance from the blast zone , you will receive an amount of damage if the randoom factor is fullfilled .
That way it would looks like it approriate even if it isn't accurate
But in order to make it accurate as some said, you gonna had too much factors to take in count . Such as amount of explosive, density of air, density of metal , how it cracles, wind, terrain , target proxy , other proxies, direction , soft protection and so on...
or am i completly wrong ?