I hear your concerns.But we have 3 military buildings,and we only use one of them.As for the anount of supplies,yes true,we are going to need a lot more,but that can be adjusted.The prosperity towers wonder can enhance your supplies spell,making you earn enough supplies for all 3 buildings.
Or better yet,the idle military buildings can be active not all the time,but let's say only during the spire event,when you do need extra troops.So only during the event you can train troops in all 3 buildings(the activation can start 1-2 days before the event so that to have some time to train).That way we can use troops that right now we don't.We have access to 15 different troops.How many of them do you really use?Just a thought
Also give an extra ability for the other 2 buildings not to be idle.For example,make them being able to produce orcs also.Caterers need orcs later all the time for tourneys+provinces
The goal of the game should be to "force" the players to use as many aspects of game as possible.What is the point of having buildings available when the majority of the players never build them?As for those who will say extra space is needed,yes true,but that can be adjusted by reducing the size of all 3 buildings a bit.