One thing that I'm discovering here lately is to take your vision and stick to it.
Initially when I started developing the stuff I've been working on, I envisioned them as sort of a slow burn; missions where I'd patrol and maybe I'd find some action, maybe I wouldn't. As I started reading and learning and picking people's brains, I started adding more and more forces (because that's how most missions are built) until things more or less resembled a COD mission. Not what I'm looking for!
Now don't get me wrong, this is still a video game about killing stuff so I will still have more enemies than typical real life patrol missions (certainly a shit ton more), but I've been pruning a lot in the last few days/weeks and I'm having that sense of wandering and discovery again. Still by no means perfect, but more more in-line with my original goal.
I also was beginning to make this stuff for SP-CO16 which is nuts (for me) in hindsight. I generally play alone with AI so am now shooting for a SP-CO8 experience.
I typically make Assymetic Insurgency missions. This means OPFOR (the Assymetric side) will recruit forces from the civilian population; meaning the force strength they start with can dramatically increase/decrease depending on how well me and my BLUFOR mates do our job. This is a great concept and only possible thanks to the power of ALiVE.
I've been finding balancing the missions for total units on the map has been easily the hardest part of all of this so figured I'd share that. It's been a constant struggle of asking myself how many enemies I want to have per square foot so things don't get too boring and how many friendly units I want on my side to assist me when I do that. Some maps my team is part of a much larger force and with tons of action; on others, I literally use no BLUFOR AI Commander at all so it's just my squad against the world. With different missions I'm tinkering with different things.
For instance, try messing with limiting objectives a bit within the mil/civ placement modules and then go in game and watch how that impacts unit placement on the map. It's really pretty fascinating and these little decisions change the feel of a mission big time. In some missions I use "Do Not Filter" so the entire map is peppered with friendly and enemy forces. In others, I limit BLUFOR to only large objectives so they can handle the large urban areas and my small squad can handle the small towns and villages.
Lots of ways to go about it but there's lots of helpful people to help you here too if you have any questions. Good luck with your mission(s)!