One idea I currently have is to make an alternate version of this mod in which the training building requires stones to operate.

However, I do not currently know how to make a building consume materials without creating a production/crafting bill or producing some kind of output.

If anyone is more familiar with FCS than I and knows how to do this, please leave a comment or shoot me a message. I'd be greatly appreciative of any input I could get.

Any and all contributions will be noted accordingly.