This form will help you (or at least how I did it) add weapon from other squad to the one you want.

First, find your mod folder, it should be in the same drive as your game, to have a easier time of finding it. right click on your game in steam, go to manage from drop down menu, browse local file.

From there, go back up to steamapps folder and open workshop/content/1239080/33224749060

Second, find the squad you would like add the weapons to and find the unit name in units folder.

Exmaple: I want to add weapons to RussianCT squad, I would open units/unit_RussianCT.xml (I use notepad++ and VScode as text editor)
Then I would make a list with those unit class like this:
"Alpha_SQL"
"Alpha_Rifle1"
"Alpha_Rifle2"
"Alpha_Rifle3"
"Alpha_Sapper1"
"Alpha_Sapper2"
"Alpha_Sniper"

"OMON_Shield"
"OMON_Sapper"
"OMON_Rifle1"
"OMON_Rifle2"
"OMON_MG"
"OMON_Sniper"

Third, find the weapon you wanted to add from another squad, I recommand using the ingame menu to find which squad have what weapon and who they belong to. Then access that weapon script in equipment folder

Exmaple: I want to add desert eagle from AIM to RussianCT, I would open equipment/firearms_pistols_AIM.xml

Last, find the weapon and then add "to name" inside bind with new lines.

Exmaple: I would use ctrl F to look for Desert Eagle and add the lines so bind looks like this. (I also have desert eagle added to VBSS squad)
<Bind eqp="iov_DesertEagle">
<to name="AIM_Rifleman_W1"/>
<to name="AIM_Rifleman_W2"/>
<to name="AIM_Sniper_W1"/>
<to name="AIM_Sniper_W2"/>
<to name="AIM_Spy_W"/>

<to name="VBSS_00s10s"/>
<to name="VBSS_00s10Supt"/>
<to name="VBSS_00s10Sniper"/>

<to name="OMON_Rifle1"/>
<to name="OMON_Rifle2"/>
<to name="OMON_Sapper"/>
<to name="OMON_Shield"/>
<to name="OMON_MG"/>
<to name="OMON_Sniper"/>

<to name="Alpha_DeSQL"/>
<to name="Alpha_Rifle1"/>
<to name="Alpha_Rifle2"/>
<to name="Alpha_Rifle3"/>
<to name="Alpha_Sapper1"/>
<to name="Alpha_Sapper2"/>


<to name="i50AE_DesertEagle"/>

<to name="IronSights_Pistol"/>
</Bind>

Note: some weapon have suppressed version for image and possible different stats, that will be under a different bind

Exmaple: when you add desert eagle, you also would want to add the squad to <Bind eqp="iov_DesertEagleFullAuto"> for when you add full auto upgrade in game

Hope this helps :D