shop and hero unit.. is it possible?

I came up with a very interesting idea while thinking up new ways to attack..

one way is to use the "unit finished training" trigger..
I summon the attack, if you will...
once done training, the target will attack at a certain point.

So how do I select where that point is?
I decided if I can have a movable building, it could be the "triggering unit" and thus the point where the attack is to be made.

Also, I want the attacks to have cooldown...

so then..
I make a movable shop base model building.. since stock can be set to intervals. the movable shop is basically a "target" for the attacks.

Now all I need is a hero to select the shop.. that's no problem. But here's the thing.. is there a way to make a shop base model that is also a hero? The reason I need this is... a) it could select itself and b) I don't want to allow the user to train too many of these shop buildings..

ideally... I have a hero (undead so it just summons the shop target building) which is the "target controller", and it can train "targets" (the shop), but I want to limit the number of targets that can be trained, ie one.
Is this possible?

I see some work arounds.. like implementing cost to training a target.. but I'm not really fond of that idea..