There's no point in limiting Fortress at all; in WoG, it's a castle slightly above average, and the main overpowered units have been nerfed.

I disagree. Psychos should be banned from being upgraded.
A long time ago, Samurai organized a tournament called "Bay against the Russian internet." According to the rules, a bay tournament was held. I played against Markon.
The first game is what I remember.
I took Utopia with the Book of Earth and played against Conflux. Even though my stats were higher and we had roughly the same number of troops, I couldn't do anything in the final battle against upgraded Psychos (Conflux had 6th-level troops). Therefore, IMO, upgrading Psychos should be banned in WoG.
P.S. Someone might say: "Why did you trade Conflux?" But WoG and TE are designed so that all castles are equal. However, why do people still trade for the castle!