independent forces move on their own and gank the player as well if you're in a bad location. I've lost plenty of forces early game myself.

How would i go about adding the Tag that stops things like Raven Spies and Invisible Eyes from taking land?

Unfortunately, I believe the non-combatant property of the Raven Spy and the Floating Eye is among the ones for which mod commands are currently lacking.

Regarding your original question, there are some mods published by Carn for this purpose, I believe. (From what I understand, they will add some kind of guardian in each player’s home citadel, to prevent its loss to independents.)

Though another solution, which is the one I prefer myself, is of course to just add one or two players to the number you’re aiming for. So if you want 5 players, set the game up with 7 or something.

I usually start with 15 AIs on a really big map. About 5-6 generally get taken out by wildlife and failed summons, a few get killed by other AIs, and I usually end up with myself and about 4 or 5 AIs, all with reasonably stable and secure nations ('secure' in this case meaning that it takes deliberate focused effort to take them out)

{LINK REMOVED}http://www.mediafire.com/download/8lqbbd885rl28er/HomelandSecurityCo4.zip

Homeland SecurityCo4 mod
unzip contents into C:\Users\YourName\AppData\Roaming\coe4\mods

Add immobile defense to every players home citadel to prevent early AI destruction by random wilderness riff-raff. Code had to be radically changed as original COe3 mod did not work. Added another crystal and Guardian from original. Game may give AI extra Guardian and crystal defenders, not sure why, but may be based on difficulty.

Most early AI deaths now result in that class losing its only remaining commander.
Mod inspired by Ballbarian and updated for CoE4 by Stehmchip."