Isn't that $Detonation Radius?
Anyway, what if you make another missile that uses the other one (other flag, whichever that is)? So you fire an "unarmed" MIRV set to detonate 100m from the firing point. It has no explosion and spawns a single "armed" MIRV with "inherit parent target" and set to detonate 20m from the target. It would still explode if it actually hit something before arming, but I can't think of another sensible behavior in that case. Does that do what you want?
No, it's not $detonation radius, detonation radius determines how far from target it explodes. You're thinking of detonation range, which is how far from the launcher it detonates. I don't want it to detonate a set distance from the launcher, I just want it to be able to detonate at the set range from target without blowing up inside the launcher, and I wanted to have a field that gives it a portion of flight where it absolutely will not detonate, regardless of something running into it, it thinking it's within range, anything.
What I've done so far is simply remove detonation range and set the inner radius to 800 m.
Also, your suggestion would probably work, though it'd take up more weapon slots. Also, for some strange-ass reason, I have a delay of 3 seconds on this missile's swarm settings, and it launches much faster.
I'll take a look at the Hydra, and hopefully modify it to fulfill my purposes.