Monarch's upgrades are mostly fine, but the final upgrade at level 20 feels random and underwhelming, especially compared to Ion, Legion, and Ronin. Instead of granting us one perk on spawn, why not make it so that, upon finishing our three chosen upgrades, Upgrade Core cycles back to T1 and begins adding mods randomly (123,123,123). Since titans tend to last longer in FD, this is completely viable - I've gone through 12 upgrades in one match, and would appreciate the extra firepower and buffs in the last couple of rounds.
The highest I remember was 17 cores with Monarch in a single game of FD. For some reason I have some kind of itching memory waaaay in the back of my head of 60, but that sounds really much like a lie.