Hi, to prevent the player to buy snipers, you can simply rise the amount of gold needed to build it, and then, when the player has built the academy of immortals, you lower the price

Edit - Fixed both things today.

Turns out by placing the Academy of Immortals outside the red square defining the playable boundary of the map, that this disables research from the Stone Workshop. And because the Academy isn't powered, it can't grant the ability to turn regular units into veteran ones. Cool! Exactly what I wanted. Bit of a round-about way to do things but it works.

The sniper cost was not working at first because I read someone else's post where they gave an incorrect example of ApplyRules. In their code snippet they used "Gold", which doesn't work. "GoldCost" does, which is what I'm using now.