Concerning the speed reduction from wearing armour, does this affect actual movement speed or simply the speed of actions (eg. attacks or spells)? If it affects movement, would it be possible to make this penalty only appear during combat, so that I don't constantly have to wait for my heavily armoured fighters to catch up with my nimble rouges?
It's less a clash of cultures and more of the intermingling of them. Places settled by Aedyrans in the Dyrwood tend to have Eld Aedyran or regular Aedyran (i.e. plain English) names. The common names for some creatures are Glanfathan but others are Eld Aedyran or (rarely) Vailian. The cultures borrow terms from each other, too. The title of duc (ducs bels and ducs panits) is used in the Vailian Republics for the sovereign ruler of a city-state, but the Dyrwoodans borrowed it when they rebelled against the Aedyran Empire. Admeth Hadret was originally an erl palatine (palatine/palatinate also being borrowed from the Vailians), but he styled himself as a duc of the "free palatinate" during the rebellion.
Got a rush of excitement reading this. All the hints of a new and unexplored world, and not too far from now I will visit it!