With a global mana system, we gain the ability to have strategic spells be caster independent.
It also opens up a lot of very important game elements for the AI as well as the player in terms of making spells have more "interesting choices" such as:
- Spell cool down (N turns before being able to cast again)
- Turns to cast a spell (a spell that takes N turns to cast)
The reason these two things become possible is because in Elemental v1.0x, your maximum mana was tied to the caster's essence.
In v1.1, magical essence is a boolean (you got it or you don't). Anyone who has magical essence can thus draw magic from the global pool.
Children of sovereigns become crucial because unlike imbued heroes, they naturally have essence (so there is no imbue cost associated). It also opens up the possibility of being able to use stored mana for enchanting items or forging tools and such in the future.
Now, while you humans may find this stuff "fun" it's the AI that benefits the most from it because I can write the AI with a system where there's a specific goal -- maximizing mana production. Plus, if a channeler can cast strategic spells into a tactical battle even if he's not present, it justifies putting lots of time into intelligently choosing which spells to cast.
I.e. if I, as a developer, KNOW that magic can be part of every battle, then it justifies the time to create and use more interesting spells.
Now, someone might/should ask, why didn't we have this from the outset? I'm sure some beta testers suggested something like this (MOM had this). I really don't have a good explanation other than to say that we fell too far towards the RPG line of thinking -- treating each unit as if it were an RPG character rather than thinking of your kingdom strategically. In short, we really wanted to find a way to have our cake and eat it too but you know what they say -- even when you don't make a choice, you're making a choice. In this case, not biting the bullet and being decisive in making magic a strategic game mechanic rather than an individual quasi-RPG with some strategic mechanic has been crippling across the board to the game's overall design.
There is no "magic bullet" of course but nearly all mechanics, balance, etc. flowed from the decision of having mana tied to individual magic casters rather than having them make use of a global pool that is derived from a single source (the channeler sovereign). With everything revolving around a mana limiter that can only be raised individually by going up levels, you cripple the scope of magic and in turn the combat and the variance in the world (i.e. things get boring).
Worse yet, the per unit mana limit in Elemental v1.0x also limits modding because modders too are stuck with the same problems I run into -- all spells have to be between 1 and 15 or so mana. Look at the change to teleport -- 15 mana. Not that big of a deal if you're using a global mana pool but it's a big deal if you max at say 12 mana because of an essence block.