Total war. Knightly orders, wizard units, clerical support, peasant levies, shadowdancer assassins, teleport strikes, evening green slime bombings, blights, incorporeal undead plauges, inhuman allies, giants as artillery, manticore air support, frenzied berserkers on unicorns, warblades and marshals leading charges, elemental and xorns engaged in deep earth sapper battles, weather control, hostile wishes, helms of brilliance, iron golems on the front line, dragons battling in the skies, sauguin raiders vs merfolk defenders battling over shipping, gated outsiders, summoned godly aspects, the unleashed might of an elder Druid, werefolk hired to give quick powerups to legions of peasants, trolls used as siege weapons, artifacts unleashed, sladdi dropped behind enemy lines, deals with devils, angelic counterstikes, war elephants, doppleganger agents, alt-prime mercs, temples desecrated, half-dragon rustmonster breeding programs.....
Depends on how the level of magic in the campaign. In a relatively "low magic" campaign, of Tolkien-level magic or so, a lot of stuff just woulldn't happen.
My campaign is Greyhawk-level magic, which means much of that could and would happen except: warblades and marshals (I ban most Prestige Classes, as I don't see a need for anything beyond whats in the DMG), xorns are unlikely (not sure how you'd get or control one), artifacts are unlikely but interesting, slaads and devils/angels are not going to happen in any significant numbers, dopplegangers have no reason to work for humans, and half-dragon anything is completely banned.
Otherwise, it sounds like a lot of fun to me.

Consider your ideas snipped.