I think one of the few things that really frustrated me in the last insurgency game was lack of thoughts behind certain maps for certain game modes.
Obviously, I know that NWI has worked very hard to balance the maps out post release on many occasions. However, I do still feel that they are going to make the same mistakes they have made (and possibly more) so these are some general things to keep in mind when map making.
Balance for SPECIFIC game mode. I know NWI has made significant changes to balance out the Push game mode, but not much else. For instance, Burhiz strike is so easy as attackers, I've rarely ever seen a victory for defenders (and push is also a little unbalanced for attackers but not as much). Another example would be tell/station - occupy, where it seems like the maps were designed for push, and Insurgents get the upper hand for their defensive positions. I am glad at least they have separated firefight and other game modes, But I would like to see that trend more, with more balance towards each specific game mode. I would go further and add the vehicles and call-in supports as well, but perhaps they could use another game mode to thrive in.
ALWAYS have both flanking routes (at least 3 entries in total). It seems like some maps such as Summit push (Security attacking, point B or hideout security attacking A) has only pseudo-flanking routes which is actually impossible to use as flanks, and only one flank is available. This also adds to the fact that one angle can block several "lanes" which nullify the existence of flanking routes to begin with as well.
Use Map design to protect spawn, NOT by restricting area and alike. Many of the current spawn locations seem to be in a wide open area and can be spawn camped easily if someones sights allows it when they get out of the spawn. Spawn camping will always be a thing in this game, but that doesn't mean the maps should make them easy for someone to do so. It should be as difficult as possible, Especially since fire-supports are a thing, and since DOI, a spawn wipe from a single air strike happens quite often.
One solution would be to have a spawn inside a safe cover (preferably inside a building of some sorts) that cannot be seen from distance, then leads to a diverging lanes in which at least 3 paths are available before ever coming into sight of the enemy, with multiple barriers to block bullets and line of sights in between, without having to go all across the map 90 degrees from the objectives to do so.
Cache, fuel truck locations. Since rocket launcher paths are straight and accurate, it is extremely easy (especially for Security with M3 MAAWS) to snipe these things. Caches should be secure in hiding (without windows to RPG snipe them) and trucks should be in sheds that cannot be sniped either.
If these are well implemented, the unnecessarily restrictive "No-go Zones" can be more flexible, and defenders can push out a little more for preliminary defense.
Side Note: I know that the game will launch very soon, and these will not be implemented immediately even if they are heard, but I will also add a little suggestion as well: I think currently, maps for push and skirmish can be a little reduced and vehicles and air-strikes (artillery are fine). However, the map assets can still be used in future game modes that has a larger scale. Such as attacking an artillery fire base/air field to silence them for call-outs, with more time limit, waves and grander scale. Or a game mode where a convoy of vehicles move along a path into an ambush, where one side has not many waves, but has fire support and vehicles and trying to escape alive, and the other is just trying to stop them etc. But I think all current game modes are set up for a CQB environment like the classic insurgency, and hence why people say they feel that it "doesn't have the feel" to it.
Edit: the spawn protective design is especially important due to the bloody fire support that commanders spam on enemy spawns. The helos are a nightmare when you have just spawned in as insurgents.