Yeah I think I can help with this when im home. Just have to try modifyng one thing to make sure it works.

Alright here we go, it looks complicated but I just have a tendency to put a ton of information since I don't know your experience level with scripting.

First you need to define this function which you can do just by placing it in your init.sqf ( I usually put it at the bottom so you don't crowd the file (and so the sleep command which is explained later doesn't hold up the bulk of your init.sqf)).

cjb_addObjectiveToSides = {
	private["_objectiveParams","_factions","_faction","_opcom","_opcomSide"];
	_objectiveParams = _this select 0;
	_factions = _this select 1;
	{
		_opcom = _x;
		{
			_faction = _x;
			_opcomSide = [_opcom,"side",""] call ALiVE_fnc_HashGet;
 
			if( _opcomSide == _faction) then {
				[_opcom, "addObjective", _objectiveParams] call ALiVE_fnc_OPCOM;
			};
		} forEach _factions;
	} forEach OPCOM_INSTANCES;
};

Then, also in the init.sqf you need to do this for each objective you are going to add

[["obj_1", getMarkerPos "Markername", 100,"CIV"],["WEST","INDEP","EAST"]] call cjb_addObjectiveToSides;

For each objective you will have to change a few things to make sure they are each unique

1. "obj_1" -- this can just be changed to ex. "obj_2" ,"obj_3" just add 1 each time you add another objective

3. 100 is the size, you can change the size up or down depending on the size of objective you want

4. ["WEST","INDEP","EAST"] This is the sides that the objective is made aware of to, the current setup will do it for all sides. However, if you make it ["EAST"] then it will only be made aware to the EAST side. If you make it ["EAST","WEST"] then both EAST and WEST will attempt to occupy the objective.
-----------------------------------------------------------------------------------------------------------------------
An example of this being used is

[["obj_1", getMarkerPos "Marker1", 100,"CIV"],["EAST"]] call cjb_addObjectiveToSides;
[["obj_2", getMarkerPos "Marker2", 100,"CIV"],["EAST"]] call cjb_addObjectiveToSides;

This will make two objectives at Marker1 and Marker 2 with a size of 100 square meters that is only occupied by the EAST side.
2. getMarkerPos "Markername" , you need to change "Markername" to the marker where this objective will be added -- this defines the location of the objective

IMPORTANT
Since ALiVE initializes during mission init, if it is called immediately it will fail since ALiVE has not initialized the OPCOM (Military AI Commander) module yet. To get around this ( I couldn't figure out another automatic way) you can simply put a sleep command before calling this.You may need a longer sleep time if your mission takes a long time to load, haven't really tested it so I am not sure how long on average ALiVE would take to initialize.

sleep 60;
[["obj_1", getMarkerPos "Marker1", 100,"CIV"],["EAST"]] call cjb_addObjectiveToSides;
[["obj_2", getMarkerPos "Marker2", 100,"CIV"],["EAST"]] call cjb_addObjectiveToSides;

This will create the objectives 60 seconds after you press "Launch" in the Editor/MP.

I'm pretty sure there is a function that checks for when ALiVE has finished initializing... something like this:

waitUntil {!isNil "ALIVE_profileSystemInit"};

Not sure if that's right however.. might have to wait for a dev to respond.

That would be much more useful.. can test later to find out if it works. I assume it will.

I know I've seen it somewhere but can't find it in the wiki.. might be in a demo mission.

Works beautifully, thanks Savage.

This would be the updated example, you can remove the sleep in the waitUntil but I figured I'd throw it in there since you said your missions sometimes take up to 10 minutes to load (so no reason to check every frame as it is kind of pointless).

waitUntil {sleep 10;!isNil "ALIVE_profileSystemInit"};
[["obj_1", getMarkerPos "Marker1", 100,"CIV"],["EAST"]] call cjb_addObjectiveToSides;
[["obj_2", getMarkerPos "Marker2", 100,"CIV"],["EAST"]] call cjb_addObjectiveToSides;

Are you using the waitUntil {sleep 10;!isNil "ALIVE_profileSystemInit"}; on the line before the objectives are being set?

That is exactly that is supposed to prevent, so if it is still happening not sure why.

It's chucking out an error because ALiVE hasn't fully initialized so OPCOM is still undefined(I don't know the complete details).

I don't think so atm. I believe this was one thing they were looking to change in the future because OPCOM always prioritized the same objectives every mission with little to no randomization.

Edit: Here's the DH ticket
http://dev.withsix.com/issues/76102
Edit: Ticket has been closed and feature will be available in next release.

What Friznit said is correct so I'll see if I can tie any loose ends together so you may not be as confused on certain things going forward

The script that I was explaining above was actually a community written script (cjb_addObjectiveToSides) to add an objective mid mission. To use it you would have to define it first by placing it in your init.sqf or placing it in a file and then calling that file from the init.sqf. You could then input the parameters that the script would use to add an objective and it does the rest for you.

Example: [["opforComRetake_obj", getMarkerPos "opforComRetake", 200,"MIL"],["EAST"]] call cjb_addObjectiveToSides;

Params:
[[_objID, _pos, _size,_type],[_sides]] call cjb_addObjectiveToSides;

_objID: String , "name" of the objective
_pos: Array, position the objective will be added
_size: Number, the size of the objective
_type: String, MIL or CIV >> the type of the objective
_sides: Array, the sides that the objective will be made known to, each side must be wrapped in quotes

Here's another example

[["letsAddAn_obj", position player, 100,"CIV"],["EAST","WEST"]] call cjb_addObjectiveToSides;

--

Is there an explanation of syntax somewhere in the online ALiVE instructions? For that matter, it seems like there is no real manual for ARMA 3 sqf scripting, other than the usually-not-helpful BIS wiki for functions (which is like writing an essay using a foreign language dictionary with no grammar, when everyone else has been speaking and modifying the language for 12 years). I'm getting tired of making Frankenscripts that don't work. :P I tried using Zenophon's framework (great documentation), but would prefer to throw some ALiVE modules in and just play.

Yeah scripting is hard to get into, especially when you have no real background on it. The way I learned was by scouring the wiki and just getting a big picture in terms of what commands I had available to me. Writing scripts is hands down the best way to learn imo. I had barely any clue what to do in terms of scripting until I sat down and made a simple (player controlled) suicide bomber system which introduced me and familiarized me with how variables can get passed from one script/function to another and even return a return variable. From there I kept going forward with slightly harder scripts, each one focusing mainly on a new command that I had learned that I thought was really cool, such as "Switch", "setVariable/getVariable","if/then/else".

My preferred way of learning SQF is just by trying first hand to put scripts together and by taking a look at the scripts of others who have done similiar things. I am pretty good at reverse engineering so imo that's a pretty handy tool to use especially when the community has such talented scripters.

Good luck!

Yep that's correct, mil/civ placements won't place units at Custom Objective modules so you'll have to use it's built-in unit spawning options. It will receive reinforcements though as you also stated.