[Slick]

I'll take a swing at this one.

First of all, if we define "essential" as "necessary for the game to work right or be fun" the answer is no. The unmodded game works quite well. That being said, there are lots of mods that make the experience even more fun and different to extend playability and also AI performance.

Second, as for "fun", that is very subjective. Basic recipe is to try mods, evaluate them, and play them if you like them. In general, most mods are very well done and you will be hard pressed to have time to play everything you like.

Slick.