I admit I haven't read the whole thread, so I don't know if this has been discussed:
I really like the idea of implemeting the Global Mana Pool (GMP). It allows for a lot of options, tactical and strategic choices.
The Role of Essence:
Suggstions / Comments
A caster's essence controls the amount of mana that caster can channel. This opens the option for Caster-based use of tactical spells (like MoM), and allso allows for controlling the power of spells by mana cost. All mana is drawn from the GMP.
Options to consider:
A. The caster can cast any spell with a mana cost less than or equal to the caster's total essence. There is no cap on how much that caster can cast per strategic turn - all mana is drawn from the GMP.
e.g. Urrumi the Sovereign has 15 essence. In each tactical combat turn he can cast a spell of up to 15 essence, as long as the global mana pool can support it.
B. The caster can cast any spell with a mana cost less than or equal to the caster's total essence. The caster can channel mana per strategic turn in an amount equal to his essence. Mana is drawn from the GMP.
e.g. Urrumi the Sovereign has 15 essence. In a single tactical combat, he can cast any combination of spells whose total mana cost does not exceed 15. These spells can only be cast as long as the global mana pool can support it.
C. Consumables that currently restore caster mana instead add to the GMP either as a one-time boost, or as a per-turn resource.
The caster has an personal mana pool equal to his essence. The caster can cast any spell with a mana cost less than or equal to the caster's total essence. The amount of mana channelled in combat is based on his personal mana pool.
The GMP under this option is primarily for global spells, or for global spells castable in tactical combat (as in MoM).
Essence under this scenario serves both to restrict the potency of the casters spell (cannot cast a spell with a mana cost higher than the caster's essence), and to restrict the total amount a caster can channel over a number of turns, based on his mana regen rate / implementation.
A. The personal mana pool regenerates independtly of the global mana pool, at a rate determined by the developers. (e.g +1 per turn).
i. The caster cannot cast if his personal mana pool is empty. OR
ii. The caster can cast if his personal mana pool is empty, drawing instead from the GMP (likely at higher cost).
B. The personal mana pool recharges fully between turns, drawing from the GMP The caster can cast an amount in combat equal to his remaining mana pool. A couple of possible implementations depending on how much casting the developers desire:
i. Caster mana recharges slowly in combat (e.g. 1/turn), drawing from the GMP. OR
ii. Caster mana only regenerated out of combat, between turns, drawing from the GMP.
iii. (OPTION) Caster can cast when out of mana, drawing from the GMP at higher cost.
C. The personal mana pool can be recharged on demand, drawing from the global mana pool.
i. Caster mana recharge is possible on both the strategic map and (potentially at higher cost) from within combat.
ii. Caster mana recharge limited to the strategic map.
iii. As (ii), but allowing the caster to channel from the GMP once his own mana is depleted, at higher cost.
D. A combination. Each caster independently regenerates their personal mana pool, but can also tap the global mana pool to recharge at a faster rate, either between combat or just on the strategic map.
E. Consumables such as currently exist can still be used to restore caster mana.
#3: Strategic Spells
A. All strategic level spells are caster-independent and draw from the global mana pool. Imbues and the like are either limited by the casters essence or alternatively, lower the casters essence by a set amount.
B. Some strategic spells are caster dependent. They still draw from the global mana pool, but require a caster to cast them.
C. Some strategic spells are caster dependent and draw from the caster's personal mana pool.
Well, these were my thoughts this far. The developers really have a lot of possible directions to go with this - spell costs, mana sources and regen can all be balanced based on the implementation chosen.