I'm a fan.  I have hope.  I have faith.

With that said, why not just change "shard" to "node" and be done with it.   Call whoever owns the microprose MoM license and buy the rights to it.  It worked.  It would work with this system, and if all other changes flowed into that path it would see success.  It may/may not become a classic at that point, but its easier working from an established baseline.

Alternatively (and I'm repeating myself like a broken record) - make the sovereign, essence and shards the unique aspects to your game.  There are a ton of games around with resources, champions, buildable cities/units, etc...  stand out like I thought you were going to initially.

Have a global mana pool, it makes sense from a design and strategic perspective.   Take sov, shards, essence out of the equation.

The sovereign is your customizable ruler.   Done in other games, a fixture here, and a good design base.

Shards are essentially just another resource, and can be abstracted as needed but unique usage to the game:

• Mana focus (i.e. more mana)
• Unique mana (separate mana pool)
• Spell modifier (pure damage = boring, add affects)
• Spell requirements (x spell requires y shard, hopefully adding in more mana and affects)

Essence is another resource, but by making it a unique stat to the sov it can be a unique parameter to the game - making the sov unique, and thus the game unique.

• Make essence be a finite resource, only available to the sov and his children
• Game setting to see how much essence is assigned to each sov at the beginning of game (0, 5, 10, 20, etc)
• Essence is your "godlike" ability and can be used strategically, but once used is gone
• Essence is lost upon death, at 0 essence your sov is gone for good (essence bearing children can inherit).  Say 1/4 total essence lost. Possibly a game setting as well.
• Essence can not be regenerated, although high level quests may have a special way of gifting limited amts of essence.  Possibly allow the absorbing of unused sov essence if sov kills sov in a special way.
• Passive/unused essence gives some bonus to the sovereign (heightened stats, combat ability, administrative ability or magic ability, customizable with sov creation)
• Essence can be used in many strategic ways - using essence permanently
  • Creating fertile land for starting a city (allow pioneers to build un-expandable outposts for influence, but need fertile land for initial city, food for growth)
  • Creating items, possibly artifact level items compared to normal magic items created with just mana.
  • Casting big spells (Big summons, entire map spells, tile changing spells, etc.  Possibly add an essence cost to teleport, i.e. something like .5 essence.  Limited, but still useful).  Possibly have a separate essence spellbook.
  • Enhancing cities (possibly also calling resources into being)
  • Imbuing champions to allow them to draw from the global pool.  Initially at X rate (maybe wis/2 for tactical mana pool) or X initial amount.
  • Possibly have essence be needed to "win" a shard.   Using above example, maybe you get 1 function when you just get a shard, but with essence you can increase that function or gain new functions.   Again, investing in your infrastructure.
  • Other ideas I can't recall at the moment

Essentially make essence a key strategic feature, everyone has it but how they use it can change the course of their game.

I'd buy that game.