It sounds like a reasonable concept. There are of course other mods that you should look at, for instance Vlad mod, Lithuania mini-mod and Anno Domini of course. The first two of which concentrate rather biasedly on specific geograohical areas and their factions which are good in their way but are a bit unbalanced. AD as you probably know is more involved in campaign map modding, and general 'historical feeling' another thing you should look at.

I would be more than happy to advise/research for Scandinavia and the Baltic, I have been trying to get a mod together with other Scandinavians and Brits recently, that would focus on historical accuracy and start in particular with Northern Europe. These are some of the areas we were planning to enact. Perhaps some ideas might be useful for you when considering your aims.

*Start year includes historically developed settlements, forts, armies, families and roads etc. E.G. The catherdrals in several Russia states

*Get rid of the New World and restart from scratch, add Iceland as a province of Norway along with the Hebrides. -Add the east coast of canada and new england?

* Add Norway, Sweden, Lithuania and several others as new factions

*Add Hanseatic League as a guild for Baltic and British Channel port settlements.

*Add several settlements to northern Europe and Britain (mainly Scotland) such as Ladoga, Gotland, Kalmar, Kongahelle, Jelling, Lejre, Bergen, Ostfold, Vestfold, Stirling, Perth, Berwick on Tweed, Hebrides, Iceland etc.

*Historically accurate ownership for Scandinavian kingdoms and Scotland at start date, such as Sweden's faction start capital at Skara, Uppsala as a rebel settlement. Gotland for Sweden, and Ladoga in Russia. Kongahelle in Sweden for Norway. Flanders for Denmark.

*Buildable pagan temples and units dependent on pagan buildings in early era for several factions. Has Unique Units recruitment benefits, Morale and Authority benefits whilst negative effects (if Christian factions) on religion. Lithuania and others which are perhaps to be pagan factions can also build Christian churches, again with unit and trait benefits but with negative effects on faction's official relgion.

As you can see we have been planning to start a 'first wave' with reshaping the game from the north downwards. We were then talking about looking at the east, Russia as a whole 'new' arena for the campaign, lengthening the map eastwards and looking at the Steppe factions. Ending the map in the east on the open Steppe before China, and including therefore the whole of Persia and Arabia in the southeast up to India. Natural 'ends' to the map.
We have discussed without any concrete aims what we should do about south and central America.