Using replaceable textures to swap unit skins during gameplay

I have scoured the forums and haven't found any answers to this so I will pose this question to the masters. Using the Mountain King as an example, he has 2 textures he uses for his basic skin, 1 out of avatar morph, and 1 in avatar morph. His mdl file lists them plainly and when triggering his avatar ability you can see him swap skins. How is this done?

The purpose for this would be to have a hero that say for example bought armor or received an armor upgrade, his skin would switch to a unit skin of the same type, but armored. I realize it is possible to make a series of models each with a different skin and replace models, But that can add a lot to a map, ya know?

Just a push in the right direction would be a big help.

It's a smart idea, but sadly, not very practical. The mountain king (and any unit that morphs) has specific animations for use in its altered form. The reason this is done this way is that textures can only be changed at particular keyframes (in animations, in other words).

Theorically, it's quite possible to make a unit with animations like this:
stand
stand gold_armor
stand iron_armor
stand dragon_armor

etc

and then tell the model to use different textures during different animations.

You can see, though, that since the model format is incapable of duplicating things, that the size of such a model would be enormous. And that's even before you consider the size of the skins thmeselves. You'd need one animation for each different skin. Sadly, there's no ability to tell a model to play a stand animation and vary the skin - you have to create an entirely different animation. Or do what you already suggested, and use multiple models. There's really no way to avoid taking up a lot of space, as far as I know.

when I opened up the Mountain King mdl and walked through what you said I can see it. I was pretty successful with helm, boot, and gauntlet models as attachments, so maybe I can step it up and do what I need to do that way. I was, of course, just looking for a shortcut. Thanks for the help