Okay so, Is it possible to add/remove packages to an actor in game via scripts?
If not what would be the closest way?

You could make a quest alias with the new package stack. You can then fill the alias "on the fly" with whatever NPC you want.

- Hypno

What Hypno said. At this moment in time you cannot add packages to actors through script.

Looks like experimenting time then

I think I may have worked out the part I needed help with:
The idea was to build upon my Dwemer Control mod. In this instance I wanted the spiders to be able to protect an area without making a new spider.
So for the hold position/guard package I am thinking of using a (unused) skill stat as a way of determining if the package should run. (And creating a guard marker underneath the spider).

Thoughts?

Well, you should check out my mod Nature of the beast II. Through the mod you apply packages to many actors like summoned creatures/followers/wolves and werewolves. All source code is included. This way I can control the actors and give them simple orders like wait, wait there, follow me and forward. I can also order them to attack specific actor and many more things (squads/aggessiveness).

That being said I think there is no point in repeating my tedious work. Perhaps we could cooperate and make our mods compatible. For example I cooperate with PsiSoldier - author of the Psikotics Necromancy Mod. He makes (summones) the skeletons and I allow the player to control them. The effect is spectacular I also cooperate with rongphale - author of the Horseman - Mounted Combat Enhancement so via my mod you can control his mounted followers. A very nice thing.

I'll have a look over it and get back to you.