I think these are two quite different things. I'm not saying both aren't (as) viable choices, but they certainly are different and the choice should be made for a reason.

If the rounds just drop in some random non-pattern, hitting and destroying the target is a matter of pure luck. Basically, you do something, and it happens or not.

If at least one round is guaranteed a pretty much direct hit, hitting and destroying the target is similar to shooting it or taking it out with a grenade. You do something, and it happens.

Personally, I prefer carefully enabling players just the right amount. A little chaos and randomness can be fun, especially in a game about war, but I think it's very easy to overdo and thus shouldn't be done without a very spesific reason. Even the tiniest details add up.

In the end though, the outcome might not be that different.

Scattered one time hit around the machine gunner target will likely eliminate the threat at the target also, or at least it should slow it down, make it temporarily unable to see / stun it if such condition is added to soldiers. There should be this specific sound when the grenades are approaching so that the high value target might realize that they are in trouble, giving them opportunity to move and take prone and find a better cover. It should actually be fun that you don't always succeed with the strike with absolute certainty.

Also I think scattered one time hit would bring more variety to the game, bringing a long range inaccurate element, as you already have hand grenades and shooting which are accurate low range.

The targeted hit bounding here and there in intervals will either scare the enemy away, kill them or slow them down, so not much difference there in the end.

Semantics I say. The main difference here seems to be the time how much does it take to carry out the strike.

I see a fundamental difference. My suggestion clearly shows everyone on the screen what's happening and what's about to happen. And the end result will always be that either the target decides to move, thus exposing itself to be shot, or the target stays put and dies... Except for the very rare occasion when they just luck out and don't die. Anyway, the point is to nudge a deadlocked situation forward, one way or another.

If the target is just instagibbed by the rounds suddenly dropping on them (as is the case in countless games), it's hard for me to see why they wouldn't think "oh fuck this shit, instant death which had nothing to do with enemy player skill, now that's just lazy and flawed design". The AI won't care, of course, but there are other implications; if the rounds miss, it's basically if nothing had happened, a disappointment to whoever called the strike, and the situation remains in deadlock.

Furthermore, I don't see any reason why the random scatter bombardment would be better (other than it's more random, but I don't think it's a clear cut benefit).

Maybe I should just start scribbling notes down and wait for the modding tools

I suppose there's also the option of providing several kinds of indirect fire for different uses. Accurate, "walked in" fire for precision strikes, basic area bombardment for instant effect, harassment fire for 30 seconds or so, whatever would be considered fun.

As I said, I don't care much myself, I'm fine also with the interval rounds that slowly creep towards the target. It's a little bit more work, like 15 minutes more work Well, it's more than that if the AI that's being targeted needs to attempt running away from the strike.

But I still fail to see the big difference in the outcome You said yourself that the rounds can miss the target with both solutions, so in both there's a slight chance of "it's basically if nothing had happened, a disappointment to whoever called the strike, and the situation remains in deadlock.", right? And for the both solutions it's valid that you probably die if you start running as you get shot and you most likely die if you stay, right? Either way you'll be dead most probably, so it doesn't do much help there to have seconds of time to notice that there are grenades coming down your way. I don't think the creeping strike is that far from "instagibbing" like you put it, it doesn't make it much different being "gibbed-in-a-second".

I'm pretty sure the player, who's getting dropped the grenades on, won't think it's fair in either mode, so there's not much you can help there when dealing with a power strike like this.

But, you anyway die in the game a lot, so what's one death more there, not much.

That would be fun, different grenades for different effects on soldiers and armored vehicles, putting a lot of area under smoke with smoke grenades, etc... But, the second it goes to that you have to create a separate UI for player to input all that stuff, types, modes, etc, it becomes a bigger feature which isn't that simple to implement anymore and tradeoffs need to be done with other features.

To some, it might become a little too much micromanagement, as you mostly just want to pour some grenades on their heads to clear the space or to eliminate a specific target

I'd stay on the simple side of things for as long as possible.

The difference in outcome isn't supposed to be huge, although I don't know how big a chance in surviving you're thinking about. The way I see it, it's probably best if the chance is so small it feels like a crazy fluke. If the same certainty of death is applied to rounds falling on you without warning, it's just... Hugely frustrating.

So the psychological difference is huge. Is the target given a chance to do anything or not? Killing players in a way that they have absolutely no chance of escaping is generally just frustrating. There's a world of difference between "no chance" and "a tiny chance".

Also, I think it's much more interesting and exciting for all players in sight range to watch how things play out in my version.

"Ah, someone called an indirect fire strike on them. Will they run? I better be ready to shoot if they do. There's the second round, they're still not running... Oh now they decided to run! FIRE!"

vs.

"Oh they died. Moving on."

I wouldn't add a UI at all. There almost certainly has to be a button to press to call in the strike anyhow, and the mouse pointer would probably be the aiming method. So, for example, a quick click for area fire strike, press and hold 2 seconds for a walked in precision strike. Granted, the complexity would eventually escalate, if even more indirect fire options are introduced (my favourite would be "call in an illumination round without parachute to blind a target" )

If you think about the scattered strike, I think they would also run. You'd hear the screaming grenades for a couple of seconds, realizing that you're in trouble, and you'd take your chances and try running to survive the field of explosions and risking being shot. You might survive it, I think there's a chance. It's not like there'll be thousands of grenades which drop down at single instant that covers the whole area, by leaving no one alive. There should be a couple of grenades that definitely come very near the target, encouraging fleeing, and the rest of them scattered on the area.

I guess neither side will be persuaded on this any time soon, and it's not by any means necessary either. I'm merely suggesting, the call is absolutely yours to make.

Note my UI suggestion (or, no-UI suggestion, rather) above though. Minimizing work that isn't absolutely necessary is probably the key to get as many features playtested as possible with limited resources.