I wonder how much work would be necessary to convert this mod to Civ4. Just theoretically, because I have no experience in modding at all, but I have some ideas.
There would be no bonus resources. COMM luxury resources would give happiness. Strategic resources like wood, ore etc. would give benefits in whole empire (access to certain buildings). The other resources would give benefits within city radius, e.g. might artifacts (+A, +D) would give some XP to might units, magic artifacts (+SP, +K) would give some XP to magical units, Naval artifacts would give XP to naval units, gold artifacts would give e.g. +25%...+100% to Commerce, Legion artifacts would give +50% to production rate of appriopriate units etc.
Great People: Hero of Might, Hero of Magic. When attached to an unit, they would give a special promotion (Lead by Hero of Might/Magic) with some bonuses like +50% strength, +1 speed, Blitz (Might) or a chance to spawn random spell (Magic).
Spells: beneficial ones would be permanent and attached to an unit, giving a special promotion (e.g. Haste: +1 speed, Bless: +15% strength, Bloodlust: +25% to melee attacks, Precision: +25% to ranged attacks, Stone Skin: +20% when defending, Shield: +25% to melee defence etc.). Curses would apply to all stacks (Slow: -1 speed unless already 1 etc.) but they would disappear after a combat or Dispel. Cure would be a Medic unit.
Ranged attacks (and melee attacks of Harpy Hags) could work as a certain number of free strikes (e.g. 10 but it would be necessary to test it). No retaliation would be a certain number (e.g. 10) of free strikes when attacking. Offensive units would have a bonus when attacking (e.g. +50%), defensive ones would have a bonus when defending.
Siege: Forts, Citadels and Castles should prevent melee attacks of foot/horse units until defensive bonus is brought down to e.g. 25%. Ranged attacks should be always possible, but defenders would get defensive bonus. Flyers and magical ranged attackers (Mages/Archimages, Enchanters, Titans. Evil Eyes, Monks etc.) should ignore the effects of walls (but not the defensive bonus of terrain).
S.
