Design is a matter of compromises by it's very nature.
Do we put in a bigger engine so it goes faster , or more fules so it goes further, or a bigger warhead so it does more damage?
if we give it a bigger engine and more fuel the added weight of the fuel will counteract the more powerful engine keeping the same speed and range but it will allow us to carry a larger warhead.
If we add all of this the missile will be larger and fighters won't be able to carry as many. Then the enemy only needs to counter measure 5 missiles to avoid damage instead of 10 missiles.
we could make it harder to avoid by giving it a superior tracking system,
congratulations you just designed the Harpoon!!!

see what I mean yet?
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Phil.
Trust In Me &
Fall As-well