I am not an developer or have any clue about modding but i do like to play the mods! =D
I played recently medieval 2 as an hot seat campaign with a friend, the turn on turn play was a little bit annoying. So we had an idea. We thought to keep the game turn based and let each player choose his commands simulatanously. So each round every body tells his army to march and if a city is in the way, the army fights. In case the army looses it could be added pull back to a certain point or if the army wins the command stay or keep going further somewhere can be added. Similar adding recruiting and building contracts. (The exception could be the spys moving.)But all this actions are just planned in this part and after pressing the next round button, all armies could start moving simultanously. They could possibly run each to it other, because no player know where the armies will be and each time this happens a window could come up and the players can choose flee or fight. So if both players press flee both pull back. if just one presses flee, the otherone keeps walkig. So the active turn is going to be more a planning turn and the "next turn" butten becomes a moving turn. If one player finishes first he still have to wait until the others have battled and finished there turns.
The advantages are: it is getting strategically a little bit harder to forsee the moves of the opponents. The time we wait another player to do a turn is reduced and could be sort of organised, that everybody finishes more or less similary. It could be the first multiplayer mod for lan games.
The contra points are: there will be still time to wait after one player finished and the other is still fighting or the idea to fight with one army more than one battle will get complicated.
I don´t know, if this is possible. So i just present the idea and ask what do you guys think about it and if this is possible or far to complicated to develop.
Hope to hear what you think about it!