Need map trigger, and advice: FF based map

[Pains Requiem]

My favorite featur of WarCraft is it's wolrd editor, which I am on more than the actual game. Since I can't get on BNet with tis Cd-key, I make my own maps to goof around on. I am currently trying to start a Fianl Fantasy 7 based map- Not based off the actual game itself, but creating a whole custom race, with units like this:

Soldier r1, Soldier r3, Alchemist, Gunblader, Shinra Goliath, Shinra Chopper, Black Mage, White Mage... etc

With a Gunblade hero, Alchemist Hero, and a Soldier hero.

To make the units, I will not be using any special unit models, but just regular units. Like a Soldier r1 will be a Marine, with modified stats. Simple this one, yes.

The Alchemist, however, will be a red Rifleman (chaning its color values to a red color) and givin a Red Dragon attack art, feedback, resistant skin. A White Mage will be a preist that has the Jaina Proudmoore model with autocast heal, blah blah. Too much to type out.

Near the end of the map, however, I want to insert a trigger that when the
4th enemy base is destroyed, that the 5th base and my final base where base 4 was at will spawn infinite units and they will all meet at one area and fight, with no gain or loss. Like a DOTA or an AOS effect. Little help on how to set that up?

Also, if you have any unit ideas for me, please don't be afraid to post.

Give the unit name, the unit it has to based on, then the model that will be used for it, abilities, attack/projctile art/animation- whatever, as long as it feels like it can fit into the military classes of FF7 and 8.

I am also going to create custom buildings so it doesn't have castles and farms.

ALSO:

Lets say I allow a "peasent" to build a Power Generator (which will be a custom ziggurat for the undead). What do I have to do to make the peasent physically build the structure, but still make it look like it is summoning? The way the undead buildings are produced some-what resemble the Mako that is commonplace in FF7. I have other building ideas in mind, but a little help, please?

[Dream_Walker]

Hmm. At the begining of the map, create variables and assign them to each building in the base. Then create a trigger that checks to see if the variables are alive, then set BuildingsRazed = BuildingsRazed + 1

Then in another trigger, have it say like "If BuildingsRazed = 5", then for each integer from 1 to (whatever number), create units, then assign wait commands to act as intervals.