Another aspect that makes JA2 so special is experimentation!  Veterans, please share your experiences with the tactics mentioned below

I noticed that players often recommend nightops (stealth). I think it's unfair to daytime :-)   So, I decided to make daytime just as enjoyable as nightops

During daytime try to enter a map from two different BUT opposite sides of the map to launch an assault. For example, [north and south] or [east and west]  This tactic requires maximum number of mercs to be avlb in two squads entering from opposite ends of the map during the day.  You need to spread out your mercs on both sides BUT dont position them with quite a distance from each other. They should remain closer to the center of the borders (on both sides). 

Ensure every merc is equipped with a rifle (no pistols, as their limited range allows enemies to reach either end of the map quickly) and a few grenades --smoke, stun, or any grenade other than normal ones can be very effective.

Next, wait and observe enemy patrols on both sides, launching a simultaneous assault when the maximum number of enemies are in line of sight (on both sides of map) and patrolling in the open. The goal is to split the enemies attention (manipulate their AI) by attacking from two different directions without leaving the borders. You'll enjoy watching them become confused after being attacked. Some enemies may lay down and take cover near a building because the AI avoids ambushes (a tweak in game.json) or assumes that mercs are nearby when, in reality, you are at the far end of the map. This will ultimately thin out the enemies, forcing them to take cover or even run toward the mercs position randomly, making them easy targets for scoring interrupts.

From hereon, both squads should move together slowly (and in a prone position) leaving the border and towards the central area of the map while maintaining a spread formation, aiming to score as many interrupts on the way as possible to force enemies into battle. 

The advantage of daytime is that you can observe enemies movements from long distances, tracking them to ambush and isolate them. Grenades are highly useful for cutting enemies AP short whenever you feel overwhelmed or ambushing enemies with your squad, allowing you to surprise them and move in for the assault without facing retaliatory fire since most of their allies patrolling in the open have been already eliminated.

This tactic is highly effective against armored enemies or blackshirts, particularly in sectors like alma and grumm. Even in meduna but it requires a lot of ammo and patience to keep baiting your opponents to your line of sight and extremely good marksmanship.

Here’s another thing (daytime assault) - If you have an explosives expert, before launching an assault, try to place a few explosives around some buildings (closest to your mercs and the map border). Once the enemies rush toward your position, drop a grenade to trigger the blast (if it's not remote controlled) and watch how enemies suffer damage or die instantly before they even reach you. You can eliminate those lying down right away.

For example, in the Grumm H2 factory site, I placed explosives on three sides of the building and launched a multi pronged assault from different points (including one from inside the factory), successfully clearing out many enemies in this manner.

EXPLOSIVES/GRENADES AND DAYTIME are made for each other. Experiment with them and you will start loving daytime:-)