For the areas of say farming, armor, weapons, production etc., have a "tech level". Players raise tech level by hiring scientists and funding them properly. I figure after a round of reaserch, a tech lvl might go up .1 - .3. Then you could say after every 5 lvls or so, all units gain +1 attack or something.

For the advancements like writing, pottery etc, just give em to them at certain times. A player logging on might see, for example, "The British have developed the tank." Then it would be up to the rest to buy/steal/intimidate the british into giving them the tanks. If it starts to become too imbalanced, someone else (like the Germans) might suddenly "discover" it too. This would provide more controll and keep the game more acurate (nobody will be fighting w/ tanks in 1700's like you can in Civ). When someone gets a radically new tech (like gunpowder) you could lower the tech of players (similar to the effect of phalanxes getting better against musketeers like I saw somewhere).

Well, those are my ideas. Maybe you could use some of the ideas. I hope it isnt too late. :P

Mark: I have started reading some of those models :P

Tech is in the Guide to Current Status thread under:

Technology - Research system draft (Hrafnkell)