Good point...
Hmm....I don't know.
I'll have to think up other ideas then

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EDIT: How about a Tower of Doom?
OK, here's how it works:
Basically, 16 people join up. Characters are created (the system could be unique or AD&D'ish, with AD&D classes and stuff). I'll try to keep the creation process simple.
Then, those 16 enter a Tower comprised of a series of floors. They have to fight their way to the top. They can form alliances, or attempt it solo.
That one sounds fun, IMO...
As usual, all that's left is to work out the chinks...
Character classes:
Fighter - The classic weapon guy
Cleric - Spellcaster that uses light and dark spells, healing magic.
Thief - The picklocker, stealthy guy
Mage - The spellcaster that does what the cleric doesn't. Destructive and Summoning Magics abound

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Standard RPG fare basically.
Spells: Since I'm already shamelessly ripping the HOMM spell trees...why not have the HOMM spells themselves?
Stats: And while we're at it...have the stat system too?
Battle System: Pure and simple (suggestions are welcome):
Attack - Defense = Damage (1 point must system; thus all attacks do at least one).
EDIT: Stats for each character class:
Fighter
ATK: 4
DEF: 4
Spellpower: 0
Knowledge: 0
(only atk and def grow)
Thief
ATK: 2
DEF: 2
Spellpower: 2
Knowledge: 2
(Spellpower and Knowledge influence trapsetting and lockpicking)
Cleric:
ATK: 1
DEF: 2
Spellpower: 2
Knowledge: 3
Mage:
ATK: 1
DEF: 1
Spellpower: 3
Knowledge: 3
When you level up you can allocate a stat point to any stat (except Fighters that have to pick Attack or Defense).
How Spellpower and Knowledge affect Thieves:
Spellpower: Trapsetting. The potency and duration of traps set is affected by Spellpower.
Knowledge: Your ability to pick locks is affected by Knowledge.
HP calculation: 10 + ATK + DEF
Fighters gain 4 HP per level, Thieves and Clerics 3 HP, and Mages 2 HP.
Thus a fighter has 18 HP at level 1
A mage has 12 HP
A thief has 14 HP
And a cleric 13 HP
Special abilites:
Fighter: As a fighter levels up, he/she will get various abilities...along the lines of:
Bash: Once per combat, the Fighter may stun his/her opponent. A stunned opponent cannot act, and if it was casting a spell, loses concentration.