I'm switching my vote to the second option. It's the only one that would work; the first is too complex, the third would essentially defeat the purpose of turns other than to gather troops, and the fourth would be too simple and take no strategical thought.
I don't have a set of rules yet, but I will soon; last night I had a bunch of ideas on how things might work. I'll write them down here in an unorganized clump, and then make them into a proper ruleset later.
@provinces and battles:
Provinces that are green on the map will be fought over on random plains medium or large at the discretion of the defending clan; if it is a neutral province with two clans fighting over it, then it will be fought over the medium version of its terrain. Brownish-tan provinces will be fought over on random steppe with the same qualities; and brown, being mountains, will not be fought over or occupied at all. Field battles will be fought over with the 'battle' mode.
At the start of the game, a clan may place 1 town and 2 castles on their provinces; however, there can only be 1 town or 1 castle per province. Towns on a plains province will be represented by Nord Town; towns on a plains province bordered by the sea will be represented by Port Assault; and towns on the steppe will be represented by Village. Castles on the plains will be represented by either Castle 1, 3, or 4 [determination of which castle map will be used will be figured out later, haven't thought of a solution yet.]. Castles on the steppe will be represented by Castle 2. Castle sieges will be fought with the 'siege' mode, and town sieges will be fought with the 'battle' mode. Every two turns a clan has, they can construct another castle in any province they have that doesn't already have a castle or town.
On provinces with castles or towns, the battle for this province can either be fought in the castle/town, or in the field (see above) at the discretion of the defending clan. If the defending army chooses not to meet the enemy in the field, then it will remain in the castle/town, and the large part of the province, as represented by its random terrain, will be occupied by the enemy army, meaning that after a set amount of turns the castle/town will be forced to surrender due to lack of food, but that to achieve this, the occupying army would have to remain in the territory. If it left, then the siege would be called off and the entirety of the province would remain under the defending clan's control. At any time when the land is occupied, the attackers can launch a siege [using the 'siege' gamemode for castles, and the 'battle' gamemode for towns] on the defenders; similarly, at any time when the province is occupied, the defenders can launch a sortie and fight in the field.
At the end of a game [round limit would be fifteen rounds for battle, and five for siege], whichever clan had least rounds won would lose the battle; whoever wins would win the province and any castles/towns it might have. The losing army would be removed from the map.
@armies:
Each clan would start with 5 armies, one in each starting province. They can either move these armies - each one can move across two provinces in a turn - or have them garrison a castle or town if there is one in the province; non-garrisoned castles or towns are just like provinces with no armies in them; they can be taken without a fight. There can be no more than one army in each province, unless the other army is garrisoned in a local castle or town. Every turn that a clan has, an army is generated in every province with a town in it; if there already is an army in the province that isn't a garrison, then the army will not generate.
So, some scrappy ideas on armies, provinces, and battles. Working on more.
Thoughts?