Has this been considered at all?

The problem is what about using it for setting up specific instances for each monster?  You would have to create a specific event trigger for everything whereas you could have a autocast spell and at the beginning of the turn it would cast.  So for monsters/AI you could set up a spell to create a new lair when a monster reaches a certain level thereby evolving the monster and bypassing the problem of summoned creatures dying when they thing that summons them dies.  This a way for monsters to have their own expanding areas, consider what would happen if you leave that Ashwake dragon to start having babies and then they start wandering and eventually setting up their own lairs and so on and so forth.  You could set this up for all creatures and have an evolving world instead of just what is there when you start.

This is why I suggested a strategic autocast so the variable for the wandering monsters would be on an individual basis as opposed to at the monster lair.  This would allow "dragon kingdoms" per se or a bunch of wolf dens with a primary den for the original den that spawned the first patrols upgrading into the greatest wolf or something.  This is somewhat ambitious but not more so than many other projects listed on these boards.

I attempted this but it will not according to Heavenfall.  I know about the upgrading goodie hut thing and I think its a great idea to coincide with the spawn new lair would be an incredible way to spread monster factions.  My only other idea to go with this would be to set it up that monsters get 1xp per turn in addition to also attacking each other of different types.  Beasts attack non beasts, trolls attack ogres, things like this so that in an area only one sub monster type is present but then they spawn new lairs making that area dense with that type of monsters.

Let me lay out an example.

Wolf lair.

Spawns two wolf patrols but they have a short patrol range say 3.  Each wolf patrol after a level up within the game through xp or through the turn timer for increasing monsters levels occurs first.  The patrol is consumed and they create new wolf lairs.  Now at the same timeframe that the original wolf patrols level and spawn a new lair the original lair upgrades to a great wolf lair and no longer spawns new patrols.  Only the newly created wolf lairs would spawn new patrols.  Eventually the new lairs would upgrade to a great wolf lair as well, when the time comes for the new spawned lairs upgrade the original lair then upgrades into its final form of some new lair, the greatest wolf lair or something.  This makes it that after a long time you have what I described above, mini kingdoms fo monsters without having to make monster factions and making all the things associated with it.

Bump this as well.