So I've been thinking, how about this new idea: There are shot-path indicators you see before the shot, or tracer paths you see after the shot, BUT only the person holding and scoped in with the range-finder sees them. The person on the gun sees nothing but the usual.
Thus person holding the range-finder becomes the "spotter" telling the gunner where to shoot. This way we can facilitate communication and teamwork, and provide people on the guns with helpful information that can assist them in doing their job better without making things too easy for them. It also removes the worry that people might be bored "staring" at an enemy, since the spotter will (if they're doing their job) be watching moving shot indicators/tracers and relaying information the whole time. Over time as gunners get more used to landing shots from various distances, they will adjust to the point where they no longer need the spotter's guidance, and overall skill level will most likely improve, but even for experienced gunners, you could start adjusting to more extreme ranges, like 2km+ (I know I could use some more practice anyway).
Potentially, you could also add a crosshair of sorts to the range-finder with markings that correlate to the markings on the lumberjack and hades. (Though I'm not sure how that would work exactly, given the two different perspectives, but it's the start of an idea)
Of course, the range-finder could also tell the exact range still, otherwise the name wouldn't be relevant. Which would have the added bonus of also informing people when exactly their gun is in range. Whether or not the shot indicator the spotter sees should disappear at a shot's max range is something worth thinking about. I think it would be a benefit, as multiple cones for something like a carronade going off into oblivion cold somewhat obscure vision, and it would create a nice communication dynamic of "wait for it...wait for it...3..2..1..shoot!" However, making the range-finder too powerful has been a valid concern, so it's up for debate. Alternatively, we could use tracers. In this instance however I think shot-path wins out. Tracers you would only see AFTER the first shot, which if you're trying to optimize distance for that first shot, pretty much defeats the point, and telling the exact range is something range-finder does already, so only relying on that has been proven to be unnecessary. This wouldn't necessarily be a bad thing, mind you, what it would do is make range-finder mostly a sniping tool, which I'm okay with, but I'm doing my best to try to keep everybody's ideas in mind, and telling when guns are in range was a suggested feature that people seemed interested in.
One argument FOR tracers instead of shot-path, is that this idea is inspired by real world sniper spotters, who watch the path of their partner sniper's shot and tell them how to correct if they miss.
However I personally would argue against tracers overall, as most of the shots that you would need that kind of assistance with practically leave a tracer trail already.
I've tried to find a compromise that suits everyone, but if something's wrong with it, or you feel left out, or if I could've argued my idea better (that one feels like it's always the case), feel free to tear it the usual new one.