Item tech requirements

Is it at all possible to have a shared building that makes items which obey player-specific tech requirements? What I mean is, like an orb of fire, which needs a Castle. But instead of requiring the owner of the store to have a castle, it requires the buyer (which may be any ally) to have one.

Or am I asking for something contradictory? More generally can I make any common building show different items/unit/abilities at the same time for different players on the same team???

Perhaps have 2 shops at a location, but invisible to opposing forces?

Best way to check the tech requirement is to try it, but I'm not aware whether items can actually have requirements.

Well i know for a fact that an item named Sacrifical Skull requires graveyard to buy. Also you need tier3 to get Orb of Corruption.
^ these 2 facts cause me much grief in wc3 ladder :P

Only "Items Made" can have requirements and allow the shop to be allied to the player.
The requirements will follow the player owning it, not the player trying to buy, therefore the only thing u're left with is make 1 shop for each player and adding burrow to them so only 1 is visible for each player.

Ya, I didn't add burrow, but I gave the "stores" the map ping model (giving them no model makes them unselectable), then I made them flying with no collision, maybe some other changes too, and stacked them all on top of each other. Then I created a stand-in unit with the proper model but with locust ability and put that on top of all the others. Then I made a trigger so that when you select one of those stores, if it is not your store it will select your store. That way it looks like there is just one store that you are selecting but really each player is being redirected to a different store on the same spot.

Now for some reason those stores don't show their name when you hover over them. Is that some option in the object editor? I can't find it.