If they detonate earlier... wouldn't that mean that you have less time to intercept a missile?
I've had a few instances where my SMD was just loaded in time. Firing and destroying the nuke, like... 1 second before the nuke exploded.
That's a game balance change.
Unless you slow the missile down near the end when it curves down to hit... slowing it down just enough to where it would explode in the air at the same time it would have exploded when it hits the ground before the change.
Stretching or tranlsating the damage sphere a bit to a different position would probably allow for the nuke to still damage everything as intended, fixing the issue Wheelie mentioned.